I have a 3 year old hen that a week ago became lethargic ,tail was down, not eating, barely drinking, legs and feet turned very yellow, had yellow fluffy droppings, and stopped laying. I brought her inside and started force feeding her. I examined her for parasites, and she had none. On day 3 in the house with no improvement, I put her on Oxytetracycline (a broad spectrum antibiotic). Day 5 her tail went back up, her legs went back to her normal color, but feet were still yellow and she was standing a bit more, but not moving much still, nor eating. She also stopped swallowing the food I was forcing her to eat. ( moistened crumble) This morning her comb started turning black, from the tips down. It's still red by her head and not dried out at all. Wattles are still red. She is allowing me to feed her 1 syringe of food before refusing to swallow again. Poo is no longer yellow and is pretty much water with a bit of dark green. All other chickens are fine...for now. Using biosecurity measures. It's not cold here, and black is solid, not spotted. Worried about Blackhead, as they dig up earthworms all the time...but yellow poo wasn't foamy. Help!!! This is my pet and one of my favorite chickens!