On of my hens, the Americauna, is missing the plumes on the back her neck and the top of her head. She also hasn't laid in over a month. The funny thing is, she still has the quills attached to her neck, and the skin on her neck looks fine, without any redness, but I rubbed some DE all over her just to make sure. We recently had very cold weather where the girls were 'cooped up' for several days, so I am worried about a bully. Anyway, what do you guys think? Bully, or infestation?