I've found feather pecking to be caused by lots of things. Sometimes it is boredom. Sometimes it is overcrowding. Sometimes it is that they lack nutrients in thier diet, (I get alot of this around spring time when my fowl are thinking about laying and getting broody). I have even owned hens that were just bad about picking, to the point where they couldn't be caged, but needed free ranged year round. Be sure your birds are "bug" free, both internal parasites as well as mites/lice. It is amazing how much of a toll these little blood suckers can take on a bird. Hope some of this helps, I know how sad it is to get to a pen and see what yesterday was a show bird, today looks like a plucked chicken.
CB
PS The introduction of cut veggies and fruit, large pile of straw mixed with goodies underneath, free choice oyster shell are just some of the things I have found that reduce picking in my birds.