Just to let you know, I had the exact same problem as your pictures in my entire Easter Egger flock! I was beside myself trying to figure out WHAT it was! Their skin was turning yellow, and their feathers were either falling out or breaking off. Plus they were developing scabs all over. I knew it couldn't be mites, because the symptoms weren't at the right locations for mites (the vents were completely clean and feathered all around them and their heads and necks, as well as under their wings were clean). It was at the base of the tail and went up the back. I watched the flock for hours, and I had NO feather pickers, plus my rooster is a perfect gentleman to his ladies. I just couldn't figure it out! THEN, I found the answer on a domestic bird website! It was a bird MANGE from wild birds, that can also be spread to poultry. The culprit...is a mite! Who would have known! The treatment is the same as the common poultry mites, Ivermectin every 7 days for 2-3 weeks (to kill the hatching eggs). Make sure you thoroughly disinfect your coop and outside run, as well. Not saying for sure that this is your culprit too, but don't count it out. My chickens on the road to having healthy skin again because I prayed that the Lord would help me find the answer to help my babies! He gave me the idea to look at this domestic bird website!
