I have a hen that has been laying eggs for about a month now. She has started losing feathers by her tail on her back. It has been going on for a few days now, each day she is missing a little more. She is does not have any wounds. She is one of 6 hens in the coop. None of the other ones are losing feathers. When I opened the nest box today she was in there and puffed up and made that noise that broody hens make but she did not stay in nest box. I am at a loss as to what is going on with her. Any thoughts?