I had 3 roosters and they were in the same coop together up until the oldest one died. No one ever picked on anyone because they should have picked on the oldest because he had no feet to fight back, but they didn't. Shortly after he died one of the other roo's got frostbite and I removed him so that he could heal and he was maybe away for a week and when I put him back the remaining roo attacked him and he had to be removed again due to injuries. Now I have one roo with 9 hens and he seems to be really aggressive with them. One is bald on her head and back and 3 others are also bald on their backs. Is there a cure for this?