I have the same problem. Two Barred Rocks are missing feathers on neck and bottom. They are looking very scraggly and one is now listless. I also have two Rhode Island reds that are missing feathers around their tails. Its dark here and will post photos tomorrow. However, I have check several times for mites (day and night), spread DE all over their shed, I have been feeding them high protein pellets with their layer mash (18%) along with mealworms in their scratch. I have tried everything and there is still no improvement, it only worsens. One note, I am now finding feathers in their house which wasn't happening before. I believe they were eating the feathers.
Should I change the hay in the coop to pine shavings, sand, etc.? I'm worried about winter coming up in a couple of months, but read that feathers could grow back after molting. Is this true?
I just feel so bad for them. I don't think there is a bully, since they all have bald spots. Plus, I do not have a rooster. Only 4 hens in a 10'x15' coop and outside area.
Any suggestions would be greatly appreciated.