Yes! They ended up being some variety of mites after all. I went to Tractor Supply and bought some Permethrin 10, found some diluting info after searching this forum and sprayed down my coop, paying special attention to my nest boxes where they were most concentrated (I think my broody hen drew them there). I picked up my broody and sprayed her down too, and after dark got the rest of my flock on their roosts. Reapplied 7 days later for 2 weeks to make sure no eggs hatched. I never saw any again after I did that first treatment, it was amazing and affordable too.