I am having the strangest things going on this week. We were out checking on the chicks this afternoon and my daughter noticed our largest RIR roost had something wrong with his eye, I was cleaning with a damp cloth and was shocked to discover he is missing his entire eyeball but has no other...
I'm treating some chicks with similar behavior for gapeworm. Try looking that up to see if this matches symptoms of yours. It is an easy treatment - chicken wormer form the feed store. I think the trick is not waiting too long.