With all due respect, you're missing the point...your Grey at a year-old shouldn't be eating any hand-feeding formula at all, he should have been fully-weaned 9 months ago...It's one thing to feed an adult bird hand-feeding formula when they are sick or can't eat solid food for some reason, but your bird is a year-old and is not yet weaned-off of hand-feeding formula...
Just so that everyone, mostly the OP knows, this is extremely dangerous for the Grey's health, but mostly his psychological and behavioral health. First off, his body is a year old but you're feeding him the heavy nutrition that a baby needs, so you're feeding him ten times the calories, protein, fat, etc. that he should be eating, so that's not good for his physical health...
However, parrots that do not Abundance-Wean around the correct age usually suffer from serious neurological issues, usually they become "perpetual babies", meaning that your bird will never shed his baby-like behaviors, be clingy and needy, beg for you to hand feed him, etc. for the rest of his life.
You need to find a Certified Avian Vet and make an appointment, and let them instruct you step- by-step on how to properly Abundance-Wean your Grey, because it's not going to be as easy as described above with a normal baby parrot at all. At this point he's been hand-fed for the entire first year of his life, and he's not going to give that up any time soon...And it's the action of you hand-feeding him that he won't give up, not the formula...But you need to get him fully weaned onto ONLY solid food soon, because the hand-feeding formula is made for developing babies and contains tons of calories, protein, fat, etc. that his body doesn't need, and he's now at extreme risk for obesity,
fatty liver disease, diabetes, gout and other kidney diseases, etc.
This is a very serious problem you have, please take it as such, because we're talking about your bird having been fed this for 9 months too long, and again, besides his physical health, fully weaning him EVER is going to be an extremely difficult task, and you're going to need professional help doing so...