If they are eating each others feathers it is a feed problem. Make sure you are feeding them a balanced layer feed. For some reason they are not getting enough protein. They eat the feathers because they are made of protein. Until you can verify that you are feeding the proper layer with enough protein feed your chickens additional protein.
Bake some chicken thighs, remove the bones and chop into small pieces
Black oil sunflower seed without the shell (I personally feel the shell is not good for them)
Just to be sure it is not a mite or lice problem check them for both. Mites and lice can make feathers come out too but I think your key word was 'eating'.