Hi Welshchick, A friend of mine on the allotments had the same problem recently of them not wanting to go in at night. No mites on the hens during the day but he unscrewed the roof of the coop and it was teeming with the darn things. Has decided to burn the coop have a good clean up and start again with a brand new one. He bought the old one second hand so the mites may have already been in it.
Have you checked for mites underneath the perches, this is a favourite spot. One other thought are they broody? This would not put them off going in at night of course, completely ther opposite!
