If I remember correctly an Alexandrine/IRN usually weans between 10-14 weeks old, give or take.
How long ago did your Alex start refusing hand-feeding of baby bird formula? Did you keep offering hand-feedings of baby bird formula after he refused a feeding, or did you just see him eating solid food and stop all formula feedings?
I guess my biggest question is how did you wean your baby, meaning did you place the solid food you were wishing to wean him onto in his cage/brooder while you were still hand-feeding him baby bird formula, and slowly allow him to start picking at the solid food while still hand-feeding him formula? Did you SLOWLY wean him down from 4 hand formula feedings a day to 3 to 2 to only 1 formula feeding a day, and continue to feed him/offer him that 1 feeding at night?
How much solid food is he now eating per day, and how often during the day/how many times does he feed himself? Does he ever display begging? Do you hear him whining?
It's very possible that he was not actually fully weaned when you stopped all formula hand-feedings, or that even if he did fully wean and refused all hand-feedings of formula if you actually did continue to offer them, that he has now regressed back to wanting formula feedings again. It's hard to know because you mentioned what solid food he was eating but you didn't mention how much he is eating or how often. Also, we do not wean baby parrots onto those types of solid food but rather onto pellets, seed mixes, and fresh veggies and fruits along with whole grains, so we can easily gauge if a weaned baby is not eating enough pellets/seed mix, but it may be hard for us to know what a normal amount of that food is for a day...
One thing is sure though, if he's not eating his solid food that you weaned him onto or he is not gaining weight, or is actually losing weight, something is very wrong. If you were weighing him daily on a digital scale every day while you were hand-feeding him formula you could compare his weight now to his weight during the weaning process...
"Dance like nobody's watching..."