I have struggled with mites ever since I got chickens and have even had deaths from them and I can tell you that is not mite damage. I'm not saying they don't have them, but all that baldness is certainly not down to mites alone. I agree with Ranchhand in that your coop size is way too small for the number of birds you have. I think you either need to increase their space or reduce the number of birds you have if that is not possible. I would also suggest hanging a cabbage or similar for something for them to do and saddles are a good idea to help reduce the pecking. Protein enriched treats such as BOSS and scrambled egg wouldn't do any harm either. Best of luck with the poor things!