Hello and welcome! This place is full of great people and information! Glad to have you. You have a lovely looking flock!
Your birds are probably bonded to each other--- that happens with multiple birds a lot (in the presence of birds and humans, they often show preference toward the bird). 12-18 months is also when they enter puberty, which means you are likely dealing with hormones. Keep in mind- this doesn't mean that you cannot still bond with them, you just made things very complicated by getting 2 young birds (edit- 3) at the same time. They are beautiful and healthy looking, but it's like having complicated triplets as opposed to one baby lol.
Even if 2 birds are the same gender and a different species, they can be a hormone trigger for another bird but your 2 eclectus are the same species and they are a male/female pair, which is even more significant.
Make sure you are not providing access to any even remotely shadowy spaces in or outside of the cage (no under furniture, huts, boxes, hollow object that they can put their head inside, no hammocks, pillows, blankets, under clothing, paper piles etc).
ALL birds change at puberty. All hormones are rough. Just because you are having a rough patch now doesn't mean to give up on them, but did you want a breeding pair to begin with? I am just curious because of the fact that 2 birds of the opposite gender are going to follow nature's course. Respectfully, you kind of set yourself up for this complication, but it isn't impossible to make it work and hindsight is 20/20. I do believe this is their breeding season---another member was just complaining about his bird's hormonal behavior, so things are probably very amplified right now, as they are not totally done with puberty AND it is that time of year.
They also need lots of distractions and exercise during this time---chewing, flying, playing etc. How much space to they have? How often do they get out of their cage/cages?
Avoid warm mushy food during this time as well, as it can mimic regurgitation and keep "conditions of abundance" to a minimum---birds are more likely to mate when the conditions are favorable (e.g., tons of food etc).
Make sure they are on a very solid sleep routine...12 hours each night at the same time roughly.
Pet only on the head and neck...Look out for symptoms of egg-binding if they have access to mate and make sure that if an egg is laid that you are prepared because housing siblings together will lead to incestuous bonds and other babies with genetic problems--they will need their own cages eventually--heck parents will even mate with their kids in captivity in some cases (if left together long-term). Plus the millions of other complications that come with allowing birds to reproduce---hand-raising a baby is only 1 (potential) part of the expensive and complicated (often heart-breaking) process.
How are you housing them currently? Are the in the same cage, 2 cages same room, or sep rooms? Have you had them both examined by a certified avian vet--EDIT:just saw your location so I am not sure if CAVs are a thing there--if not, find a vet that specializes in birds if you can (you want to make sure they are not carrying any diseases and that the female is healthy enough to survive motherhood).
Laying eggs can be quite dangerous for a female and it can make them even more hormonal/territorial. I don't know enough about eclectus nutrition, but in other parrots, they need higher levels of calcium etc in order to pass an egg without it getting stuck, BUT eclectus parrots have a unique digestive system and vitamins can easily be toxic to them, so make you you consult someone who knows A LOT about eclectus parrots specifically.
NOTE: You Grey will get there in 2-3 years, so prepare for that and stop doing anything that could stimulate him sexually (set boundaries now). No petting anywhere but the head or neck, no shadowy spaces etc. If you wait until puberty to stop inappropriate behaviors, it will be even harder and your bird will not understand. You do not want him to see you as his mate either (especially because he will be prone to do so if you are cuddling all the time etc. Think about human---we can take baths with kids of the opposite gender when we are babies/toddlers and it's not weird. That same (harmless) process would not be okay at age 10, of 17 lol. Birds dis;like change, so the earlier you start treating your bird like an adult, the better off you will be when the time comes. There is always a rough patch during puberty, but after that year or 2 passes, it is usually just 1-2 months out of the year that you may notice increased hormonal behavior (unless in an environment with lots of triggers).
Back to your pair--- IF an egg is laid and it is fertile, you can either let them attempt to hatch it (again, very expensive, very complicated, often very dramatic process)...But an alternative is to swap it out for a dummy egg or (sad as it sounds) boil the egg and quickly return it to the nest as soon as it is cool. Put a small dot on it with a pen in case another egg appears and you need to know which ones have been boiled. The bottom line is, if you do it ASAP, the chick hasn't developed at all. You always need to leave any eggs in the cage until the bird loses interest though, or it will stimulate her to repeat the process.
