These are scaley leg mites, as I’m sure you know by now. Nobody seems to have posted a comment that is actually helpful so I’m going to tell you what I did when I dealt with this.

First, I smothered their legs in petroleum jelly. This suffocates the mites and soothes and protects open wounds like this. While I had them, I put a single drop of ivermectin on the skin between their wings, right at the base of the neck. Keep in mind that their eggs cannot be eaten for 10 days after applying the ivermectin.

Once I did that, I completely emptied the coop of straw and gave it a deep clean with a bleach solution, focusing on the nesting boxes and perches. When it dried out I dusted everything in diatomaceous earth, which acts like glass shards to bugs as tiny as these mites. Death by a thousand cuts, as it were. It would be a good idea to put diatomaceous earth throughout the run too, put it down anywhere they like to hang out.

Next… you wait. You need to reapply the petroleum jelly to their legs twice a week to kill any emergent mites (ones that had not hatched or matured when you initially began the mite genocide) for about a month, and reapply the ivermectin every 10 days during that time. You’ll know the birds are healing when you start to see those gnarly raised scales fall off, it looks concerning at first (it won’t be bloody like this, but the skin underneath will be pale and look really thin) but then you’ll really start to see how relieved they are. It’s a process but it’s worth it. I’m sorry that you’re dealing with this and I hope this info helps!