I culled her. I couldn't take it anymore. I thought long and hard about trying to wean her back, but she was just pitiful. I had to put her out of her misery. She had pooped in the pet carrier twice and they looked completely normal. Which, eases my mind, a little. I've given the tractor a good scrubbing and after it dries I'll replace the bedding. The feeder and waterer have been scrubbed too, just in case. She was definitely the top bird so we will see what happens with the other two. I'm hoping that it was just an injury and the other two will be fine.