All, One of our three chickens (red star breed) has this leathery patch near her vent. The patch is thick, dark red/brown in color, and tough. It's not scaly, and doesn't seem to hurt her when it's touched. The other chickens aren't pecking at her there, and she seems really perky and lively. The patch is about 1.5" in diameter, and seems to be spreading around her vent. Otherwise, her vent seems normal, and she's pooping and laying eggs just fine. Pics below. Any ideas on this would be appreciated!