My laying flock, about 10 girls, have no feathers on their backs. One of the girls has quite a red back. I recently got rid of 5 roosters that were doing a number on my poor girls. Could this be why they have no feathers? How do I get the feathers to regrow? They are fed layer pellets and have fresh greens/weeds throughout the day. Fresh water 3x day with apple cider vinegar added. I spray the coup 2x per week with Poultry Protector.