One of my Wyandottes has had messed up feathers for a good three months now. She is smaller than most of my chickens, but is still fairly healthy. At first, I thought she was just molting, but as time went on, I started to get worried. About two months ago, I separated her from the other chickens, but she hasn't healed up at all! She is well fed, I give her oyster shell, sand, and whole corn, but nothing is helping her! She is still skinny, despite her being alone, still has messed up feathers, and is still sensitive to touch! I checked, and she does not have lice or any other parasite. I can't find anything wrong with her. She eats and drinks like a healthy chicken, but isn't healing! I think she was pecked at by the other chickens, and never healed or something. When I got her from a friend, she had healthy feathers, but now, obviously, doesn't. Any and all help is appreciated!