Red Fetherless Butt with white leathery skin around it "What is it"

[beeconeofhope]

Hello I was at my friends house today and she was showing me her chickens and a couple had a few issues one had a naked butt that was red and around it was white leathery skin and the others was a hen and rooster that had hardly any tail feathers and the hen had a featherless streak down her back , I am thinking some kind of feather shaft parasite. She is dusting them for that now and i gave her some DE too thats what i use on mine in there food and bedding and mixed with sand to bath in , But i have no idea what the leathery white naked but with red bung could be other than something giveing her diarrhea? Oh she said one had it's colon sticking out and she but gloves on and vasaline and but it back i am not sure if it is the same chicken or not she said it is doing fine now and it had been a while ? any info would be great Thanks so much you guys are always great!