I have about 6 each of 4 breeds of chickens, Barred Rocks,red sex links,black sex links,and buff orphingtons, and a couple leghorns. Every breed is nice and fluffy, good looking chickens, but the last couple months my black sex links look like they have mange,and terrible looking and no tail feathers. It's been very rainy here for a long time, so there is not much dust for them at the moment, but none of the other chickens look that way, indicating it's not mites. They don't seem to be being picked on by the other chickens, meaning bullying. They have full feed of layer mash, and plenty of water, are they needing some type of mineral or is it something else? thanks.