We just noticed Our previously very healthy 1+ year old chicken has lost a patch of feathers on her underside. Most of the exposed skin looks healthy except for one patch that is reddish, nothing oozing and skin is unbroken. We think she has lost some weight too. She seems normal otherwise, lays eggs, eats, drinks and moves around with rest of flock with no reduction in energy. Any ideas what might be happening and how to treat it? None of the other 4 chickens she lives with has this.