We are still working with our GCC who is a bit of a rescue but didn't pluck until he came to us. he is not bare but has a few patches that are. Our vet thinks he's hormonal (and maybe a she) and that we have provided a superior environment for him and now he's ready to breed of course we don't want that so we are limiting any behaviors that encourage hormones. Diet of course is another factor, I've read that some birds can be sensitive to wheat/corn (and a few other things) that can make their skin itchy. It has also been unseasonably cold here for quite a few weeks so the air is really dry and we can't turn up the humidifier as it causes massive condensation on the windows. So we are trying aloe spray (pure juice, food grade 50/50 or a bit more with water) to soothe his skin in case that is part of it. However, Charlie is quite a bit younger than your guy so I would imagine the hormone thing has sorted itself out already and that its some sort of environmental change whether its a skin issue, something internal or something causing stress. Good luck at the spe******t, I hope that they can give you some things to try. It is very frustrating and disheartening to have a parrot who is plucking despite your best efforts to provide a healthy environment with lots to do (funny, our guy seems to only pick at night or occasionally when we are around but not during the day when we are out and not in his cage when he wants out but can't come out - like when we are cooking. Opposite of what you would think!). Good luck with your guy. Keep us updated, I'm always on the lookout for things to try and help Charlie too.