I have a1-1/2 year old hen who has a bare spot on her back which extends a little way under her wings. I think it initially began when I had a rooster that was on her a lot. The rooster is gone. Some of the spot filled in but this last area refuses. I know it can take a while for feathers to grow out but it's been maybe three months. I added oyster shell to their food and now feed it free-choice. Hasn't seemed to help. I'm worried about how she'll stay warm this winter. Anything I can do other than get her a coat? Thanks!