Blanca, my small, two-year-old, White Leghorn hen, was under the coop, standing around with her feathers fluffed up. She's been very slow lately and, while she's normally enthusiastic about food, she hardly seemed to notice when I fed everyone this morning. I finally got her out from under the coop and looked at her. Her backside is all... squashy, yet hard. Do you know what I mean? It's sort of squashy, but harder than usual. And big. Like it's full of fluid. And her feathers back there are all gross and messy and she smells bad. Worse than usual. Like... rotting stuff, almost. And her waste is runny and she only expels it in small amounts. What's wrong with her?