I am a newbie chicken lover with a small coop and 4 hens. I have one Golden Comet hen and three Bard Rocks.They are 9 months old. The Golden Comet has laid only twice. Last week I noticed she had lost all the feathers on her underside. She is not losing them anywhere else. I have looked carefully for mites. I see nothing. Perhaps I don't recognize them? None of the other three have any loss of feathers. Can anyone help me identify what might be going on?