It is quite possible that this behavior is hormonal. However, that much plucking is an extreme reaction. I would first take him to a qualified Avian Veterinarian to rule out any physical issues that may be causing this. Birds can get skin infections, mites, parasites or other issues that will contribute to feather plucking. You also need to make sure he is getting the right nutrition. If he is on a seed only diet, then poor nutrition may be the problem. He needs to be on a nutritionally balanced diet like pellets or our whole ingredient foraging diets – Avi-Cakes, Nutri-Berries and Pellet-Berries.
If he has a bird tent or anything he seems to be sitting in a lot, remove it from him. Adult birds do not need a nest unless they have a mate and are breeding. Otherwise it can trigger unwanted breeding behavior like the aggression you have described.
Please see what the Avian Vet can find out and discuss options with your vet. The longer you wait, the harder it is to get a bird to stop plucking.
Thank for for asking Lafeber,