Do you give your girls protein? Usually its a deficiency, one of the more knowing members will stop by and give you suggestions, but I have not done this, but heard about placing vaseline, Vick's, bag balm, even shortening. The feather pickers will not like the feel of the gunk.
Also, do you feed left over veggies, fruits, oatmeal, yogurt and all that? They don't need a lot, -if you have a few birds, I should say I don't need to spare much, I give them a serving or left over peels and cook the potato peels toss in meat scraps, oats, rice whatever. Give it to them warm, and they will jump hoops for you. Perhaps not pick feathers!
Good luck!!