Could use some problem solving from those more experienced... my chickens are losing feathers on their backs. A chicken raising friend of mine said they had feather mites. We cleaned out the whole coop, treated the interior and brooder boxes with elector PSP and treated each hen with it as well. We then learned that this might not work for feather mites, so we treated the whole flock with 2 rounds of ivermectin. They still seem to be getting worse. Maybe mites aren’t the problem? I thought at first it was the rooster but he is losing his back feathers too.