We have 6 chickens (all girls) that are about 10 months old. We let them out in our yard from their run almost everyday. A couple of weeks ago I noticed that the Delaware had a bare bottom. I looked her over and couldn't find any bugs on her. I cleaned out their coop and saw nothing unusual there. I've been watching her since and have noticed new feathers coming through. Her skin is pale pink, no sores or bleeding. None of the other chickens are missing feathers. This morning I went to check on them and saw her sitting in a nesting box, but then noticed her white feathers all over the floor of the coop, they looked like they had been plucked out, not broken off. She has been laying eggs still (although the shell color is a little paler than usual) and I haven't noticed the others bothering her, in fact she's right up at the top of the pecking order. The only other strange thing I saw was the Brown Leghorn coming up into the coop and eating the feathers that were laying around. Any ideas or suggestions as to what could be going on or what I should be doing? Thanks in advance!