I need help with sick chicken!
OK also have read corid works as well? And also Apple cider vinegar to help prevent spreading?
It looks more like vent pecking to me. I would clean up their vents with a warm soak and when dry, put on some Nustock cream or spray them with BluKote. It would be wise to pen them together to heal for a couple of days. Make sure that they have enough room, get outside to range daily, and and are getting a little extra protein in their diets. Put some probiotics in their water also. Here is some info on vent pecking: http://www.thepoultrysite.com/articles/830/cannibalism-by-poultry/