My hens are missing feathers on their backs. All 3 of the Black Australorpes are like this. The Buff Orpingtons have missing Feathers in the same area, but it's not quite as many. What is causing this? Is it from the rooster mating with them or is it something else? Thought it would be higher up, if from the rooster. Don't think it's mites, and they get plenty of protein. The worst hen has recently gone broody, but but at least 4 hens out of 7 have feathers missing.