I just noticed that my budgie's cere has become very crusty and thick. I know that female budgies are supposed to have brown crusty ceres in breeding mode, but I've noticed that my budgie's cere is a lot more thicker than what it should normally be. I did some research and I found out that my bird has hyperkeratosis, which is caused by a lack of vitamin A. Is there a treatment? Can I treat this symptom by feeding her more vitamin A foods? If so, what are some good sources of vitamin A for budgies?