Thanks for the suggestions. So, if it isn't mites, you think it is feather plucking or a molt? I just want to be clear.
I have 14 chickens and 5 guineas in a coop that is 12 x 8 feet. We use two 2 x 4's for their roosts and they ALL like to be on the top one together. The guineas roost on the perches in front of/attached to the nest boxes.
The pen attached to their coop is about 30 x 20. They free-range for a few hours 2-3 times a week. They are fed laying pellets and scratch for a treat to get them back into the pen in the afternoon. They eat lots of scraps/veggies from our kitchen.
Their pen in shaded pretty well underneath large trees. And it is covered completely in plastic chicken netting (which has held up amazingly well). Our coop and pen are pretty "Fort Knoxed" out.
I haven't seen mites, and I haven't seen feather picking lately either. I have seen that before when there was actually blood on the tails, etc. But the purple spray solved that one pretty quick.
Could the redness be from sun burn? Do chickens get that?
Also, not a single Dominique has this "affliction". I have 3 EE's ( 2 hens, 1 roo) six Dominickers (5 hens, 1 roo) and 5 RIR hens. The only ones that have this "affliction" are two of the EE's and several RIR's in varying degrees. I agree that I wouldn't think the EE roo would tolerate picking. He is the dominate roo of the two. In fact, he chases the Dominicker roo around endlessly. If there were ever a roo that should be picked on it would be him. (He has this huge "hump" on his back. We didn't notice it until he was already mature. He is very docile and already has picked up on the fact that I will protect him. What a baby . . . anyway, I digress)
Any suggestions appreciated.