Saw a bunch of threads on this topic but thought I'd add another on my flock.
I have 6 hens (2 Barred Rocks, 3 RH Reds and 1 Australope) - I have a feather pecking problem I've been working on for several months. I've tried pine tar, Blue Kote, and it has not helped. All my efforts have only kept them from drawing blood, which they did one time. I managed to heal that bird. I've tried hanging liver, mealy worms, bird seed, cabbage, making more roosts, and letting them free range more often. Nothing seems to be working. Someone told me to get rid of the mean bird (one of the Barred Rocks isn't missing feathers) and I may very well resort to that. But I am currently trying to isolate it for a week and see if that helps. I'll report back how 1 week of isolation works out.