I have noticed that they peck at the coop floor a lot but have inspected many times and cannot see any red mite, but then I have never seen them as far as I know. I use diatom quite liberally so I am assuming that this is what they are eating, but as you say, they wouldn't stay in there if there was red mite. I sprayed the whole coop with some horrible stuff for cocci after treating them all the first time, but it's getting difficult to spray now with the weather being so damp - it just doesn't dry and smells awful. Will give it a go the next fine day though.