One of my female pekins is missing her feathers on her back and left side. When I first noticed it, the feathers were gone under her wing and the sight was black and blue. I separated her from the others, and after 3-4 days, the black and blue is gone. I have never seen her get picked on by any of the other ducks. The only thing I can think of is she is a favorite for the drake, and was getting worn out from his advances. I have 1 drake and 6 females. She is eating and drinking fine, and I let her out with the rest of the Pekins during the day, but she has a separate sleeping area in the coop. Any opinions?