Oh, this reminds me of a personal experience. The first winter I had chickens, they were locked in the coop/run alot because our snow was soooo deep!
Anyhow, I noticed everybody was getting a bald spot on their back, just above where the tail feathers start. The bald spot was in exactly the same spot on everyone.
Sooo, I checked everybody for mites or lice or whatever, and found nothing. I was perplexed!
What could be happening to my beautiful flock!
So it was a pretty nice day and I was outside with the flock, and I was just watching them peck around after I had thrown down some scratch for them......I watched for a long time.
AND I SAW WHAT THE PROBLEM WAS! One of my newer hens, a New Hampshire Red, would walk behind each chicken, eyeball their back, and WHAM! She would pull out a feather! Of course, they would squawk and run! I just kept watching, and she did that again, and again, and again. And of course, HER feathers were perfect! No bald spot!
MYSTERY SOLVED! I gave her to a farmer friend with a huge farm so she could run around more, and all was well again with my flock. Everybody's feathers grew back.
So this might not be a rooster problem at all.....Just take some time and observe, and look for the chicken who has the perfect feathers!
Hope this helps!
Sharon