my polish is losing feathers above and around her tail in sort of a triangular pattern. she was picked on by my other hens about two months ago and lost the feathers on a small part of her wing and on her back. the wound has since healed and there are small, dark pin feathers growing in, but it seems like a ton more feathers are now missing above that. there's basically a diamond shaped area of exposed skin going up her back from her tail. i have no roosters. she's been acting completely normal, doesn't seem sick or anything. i bought dust just in case it's mites, but has anyone ever had this happen before? i'm fairly new to chickens and this is bothering me a lot. it looks worse and the bald spot is more pronounced in person. the black dots on her skin in the first picture are the feathers growing back.