I have a flock of Americana hens. Mixed ages. I had 2 over aggressive roosters that I got rid of. The 4 older hens that the roosters were mating with had sever feather loss on their backs, wings and one tail. The roosters have been gone for at least 3 months. Theses hens have not recovered any of their feathers. The younger ones that were not mating at the time all look fine. Water is fresh, feed is ample, they run free and protected on on an acre of land. Nighttime coop is sufficiently large. I am guessing that if is was mites or lice all would be showing signs. Help!