Once a year maybe we'll have a young chicken, around 6-9 weeks old, just start wasting away. It starts out happy & healthy like the rest of its flock, but then looks droopy. When we examine it, we'll find almost no breast muscle, no real muscle tone anywhere. We're tried hospital cages, hand feeding, warm mashes, etc. but nothing really works once they get like this. We just had to put one down this morning. There doesn't seem to be any common conditions - different breeds, different sources, different coops/pens. But just every so often we get one like this. Any ideas?