I am totally clueless. I thought this was mites or lice. I have treated them , hosed and scrubbed their coop from top to bottom. I have tried DE, 7 dust, and medicine. Nothing is working. I figured it was mites cuz we had soooo much rain for the last 4 or 5 mths. But I have not found any on any of them. I clean their coop out every Sunday faithfully. I don't hose it out every week but I clean the shavings etc.
They don't act sickly or anything. They are not picking on each other. I have 49 girls and half of them have this problem. They are still laying eggs too.