I have a 5 year old layer whose first symptoms I saw were her walking gingerly like she hurt her hips. Now she's got poopy feathers. The poop is brown-I don't see any blood. It smells but not tremendously bad. I just examined her and found the skin on her bottom is black and hard. It's about a 2 inch round area and solid. I see no mites or lice. I am offering her yogurt, electrolyte & beneficial bacteria in water. Any suggestions?