2 days ago, one hen had this type of mark on the back of her comb. Today, 3 out of 4 have a very similar area. I've reviewed other pics on this forum, but have 99% ruled out mites or pox. I do think it may be fighting marks from being pecked at the rear of their comb. Suspiciously, the dominant hen has no marks yet...hmmm? Any suggestions or confirmation would be very appreciated.