I have a 1 year old white little hen called Jemima. The last few weeks we have noticed that she is losing feathers just at the top of her wing (where the wing meets the body). It on each side, symmetrical. The large feathers are going bald in that area. I looked it up and the only thing I could find on the problem was roosters, but we don't have a rooster! I thought maybe the other hens are sleeping on her but I have never found any of them sat on her. Any ideas?