I have noticed that there have been alot of black feathers in the chicken coop but since I have more black hens than any other color that wasn't too unusual BUT I think now that most of those feathers has come from one hen.......most of her neck feathers are missing...I see mostly the lighter quill making her look a bit thinner too ( I think??) so, is this normal ? what should I be looking for?? what can I do for her???