She seems to deteriorate despite your efforts. The mites will lead to severe blood loss/anaemia which needs to be treated urgently as well. Raw beef liver will help restore red blod cells.I was outside feeding her water in a syringe when I realized that she is crawling with what I think are mites. I checked when I isolated her and didn't see anything at the time, so I doubt they were the initial cause. But they're certainly not helping!
I dosed her when I put her in isolation, jic, and just did it again.
She can't hold up her head anymore. It took the other hen weeks to get to this point.
Change the entire coop and nest bedding and burn the old to kill the mites.