I'm very sorry you're going through this, but as mentioned above, you really need to think long and hard about re-homing your parrots, because the stress and trauma that re-homing will cause them is almost guaranteed to make their lives much, much, much worse, and their levels of stress much greater...And if you do decide to re-home either of them, you absolutely DO SHOULD TAKE THEM TO A CERTIFIED, REPUTABLE AVIAN RESCUE!!! You absolutely DO NOT want to re-home them to any private-party or individual unless it's someone that you already know extremely well, that you already trust with your own life, and that you know will not just take them from you and then sell them on Craigslist!!!
I have been the Medical Liaison at a very large, private Avian/Reptile Rescue for over 8 years now, and that's exactly the kind of place you want to find (I certainly can help you find the closest, reputable Avian Rescue to your town/city through our nationwide network)...I can safely and with confidence tell you that well over 50% of all parrots, regardless of their species, that are re-homed/sold to a private-party or individual or family, even when they are not advertised on shady online sales sites like Craigslist, but rather by organizations, social media re-homing sites, and private bird and parrot re-homing sites, will be re-homed/sold at least once more within the first year after you re-home/sell them....In my experience it's typically 2 or 3 times in the first year until someone keeps them for longer than a few months...And with a Cockatoo, well, they go into what we call "The Re-Homing Cycle of Hell" at the Rescue...Most Cockatoo species have an average of over 10 homes during their lives, and I have seen some of the Moluccans, Umbrellas, Sulphurs, Citrons, and Galahs that have had over 20 homes in as many years by the time they are FIRST BROUGHT TO A RESCUE!!!
Parrots are big-business right now, especially the large parrots, and they are unfortunately treated like cash-crops in the private-sale markets. So again, unless you re-home/sell your birds to a person or family that you already know very well and trust very much, then you absolutely want to take them to a Certified, Reputable Avian Rescue, because they ALL have a very long and invasive adoption-process that on-average takes several months just to get to the point where we are going to do a home visit...So that's definitely the way you want to go, because we investigate EVERYTHING about a potential adopter: Criminal Background, Financial/Employment Background, we speak to at least 3 references from their relatives, then their friends, then people they've worked with, we require a Vet reference, etc. And most-importantly require that people do at least 5 visits at the Rescue with the bird they are thinking of adopting, each visit lasting at least 3 hours, and if WE don't feel that the bird and the person or people are going to be a good match
However, as I said, it's best for the birds if they stay with you in the first place, if that is at all possible...I don't know how long you've had them, but if they are showing some Feather-Destructive Behaviors now, it's only going to go way downhill the minute they are removed from their home, from their Flock, and from you...That's just a given...
***As far as their diet goes, you definitely want to avoid any Seed-Mixes that contain any Peanuts (or other Nuts for that matter), any pieces or kernels of Dried Corn, and any Sunflower Seeds[/], because these are nothing but fat and carbs (which are turned into fat), and with captive/pet birds who aren't flying miles each day, these foods quickly cause Fatty Liver Disease, Kidney Disease, Heart Disease, and pre-mature death...And Peanuts should not EVER be given, even as a treat, as they carry a mold that is toxic/lethal to birds...
The same goes for any type of Pellets that are "Fruit-Flavored", as they are nothing but sugar, which is again turned into fat...Instead, you want to feed them a Pellet that is "Natural-Flavored"...So if the Zupreem pellets you feed them both are "Zupreem Natural", then they're pretty good, but if they are the multi-colored Zupreem "Fruit" pellets then they're getting nothing but sugar, carbs, fat, etc. from them, and you need to switch them out for the Natural Zupreem, or for a better brand of Natural pellets such as Harrisons or TOPS...But Zupreem Natural isn't that bad, it's much, much better than the Fruit pellets.
There are seed-mixes you can buy that are low in fat, high in protein, and that are extremely varied with lots of healthy seeds, grains, legumes, herbs, and veggies, with a tiny bit of fruit, but that still contain No Sunflower Seeds, No Nuts/Peanuts, and No Pieces of Dried Corn...These are what you want to replace the current seed you are feeding them for sure, I'd do this IMMEDIATELY because those junky Seed-Mixes that contain Peanuts, Corn, and Sunflower Seeds are just horrible for them, and one of the most common causes of them not living nearly as long as they should. Petco sells some really healthy, great Seed-Mixes, such as Higgins Vita-Seed California-Blend, Tropimix, Higgins Safflower Gold, etc. Whatever Seed-Mix you switch them to, remember, NO SUNFLOWER SEEDS AT ALL, NO PIECES OR KERNELS OF DRIED CORN, AND NO PEANUTS OR OTHER NUTS EITHER (There are some that contain whole in-shell Almonds, which are totally fine, the bags don't contain that many and Almonds are actually beneficial to them, but NO PEANUTS!)
*****What you also really need to make a change with ASAP is the fresh produce you are feeding them...Fresh Fruit (or any Fruit) is absolutely LOADED WITH NATURAL SUGARS, tons of them, and once again these Sugars are just turned into fat and stored in their bodies, just like the fat from the Sunflower Seeds, Peanuts, and Dried Corn is. So fresh Fruit should only be given to them occasionally AS A TREAT, NOT A PART OF THEIR DAILY DIET!!! Giving your birds a few Grapes maybe 2-3 times a week, or any other fresh Fruit in-place of the Grapes, again, maybe give them a small portion 2-3 days out of the week and that's it...What they do need to be fed every single day to improve their overall-health and restore things like their feather-quality and sheen, and just make them feel better all the way around, are large servings of all different kinds of fresh Veggies and fresh Greens, the dark, leafy Greens specifically.
Your birds should both be getting a nice, large serving fresh Veggies and Dark, Leafy Greens at least once a day. The nice thing is that besides anything in the Onion family, such as all types of Onions, Leeks, Chives, etc., which you cannot ever give them because they are all toxic to birds, otherwise you can feed them pretty much ANY OTHER VEGGIE and DARK, LEAFY GREENS as long as they are FRESH and not Canned. And fresh Veggies and Dark, Leafy Greens are very inexpensive and available everywhere, from all the Grocery stores to Walmart, etc. My guys love fresh Green Beans, all types of Pea Pods, Broccoli, all types of Squash such as Butternut, Spaghetti, Acorn, Yellow, and Green (Zucchini), all types of Bell Peppers such as Red, Green, Yellow, and Orange (they also LOVE the Bell Pepper Seeds!), they LOVE Sweet Potatoes, a little Cauliflower, Okra, Eggplant, basically any fresh Veggie that isn't in the Onion family...I would stay away from Corn and Potatoes, as neither provides any nutrition and both are full of Carbs (sugar) and really aren't Veggies but rather starches...
They also LOVE Dark, Leafy Greens, such as Bok Choy, Pak Choy, Mustard Greens, Turnip Greens, Collard Greens, Dandelion Greens, Arugula/Rocket, Chards, Endive, Escarole, Kale, etc. Stay away from any "Watery" Lettuces and Greens, such as Iceberg Lettuce and pretty much all other Lettuces, Celery, etc., as they contain no nutritional-value and are basically nothing but water...
***As far as fresh Fruit to give them as an occasional Treat, You need to STAY AWAY FROM GIVING THEM ANY AVOCADOS, AS THEY ARE TOXIC TO BIRDS, AND ANY CITRUS FRUIT, SUCH AS ORANGES, GRAPEFRUIT, LEMONS, LIMES, ETC... I know you said you've been giving them Oranges, which is okay if you only give them a very, very small piece once a week at most, but anything more than that can make them extremely sick...All Birds/Parrots have trouble processing Iron, they don't need much Iron at all in their diets, and if they are fed much Iron at all they develop a condition called "Iron Storage Syndrome/Disease", which can be fatal if not treated immediately...And unfortunately Vitamin C greatly enhances the body's absorption of Iron from any food that they eat...So this is why you should avoid feeding your birds much Citrus Fruit or Fruit Juice at all, especially Oranges, as they contain a ton of Vitamin C...So very small pieces of Orange once a week or one little drink of Orange Juice once a week at most and that's it. However, there are plenty of other fresh Fruits you can feed them as occasional treats 2-3 times a week at most, to avoid feeding them all that sugar. They like Apples, Bananas, Strawberries, Blueberries, Raspberries, Blackberries, Seedless-Grapes, etc. So these fresh Fruits make a nice treat a few times a week...
So if you start adding large, daily portions of lots of different fresh Veggies and Dark, Leafy Greens, you cut-out the fresh Fruit except as occasional treats, you switch them to Zupreem "Natural" pellets instead of the "Fruit-flavored" pellets, and you stop feeding them the junky, high-fat Seed-Mix that contain Sunflower Seeds, Peanuts, and Dried Corn and replace it with a low-fat, high-protein, high-nutrition Seed-Mix that is extremely varied in it's healthy ingredients like grains, legumes, lower-fat seeds, herbs, veggies, etc., then your birds will not only look better, they will feel a ton better and live much, much longer...