Kass, I went to bed with plenty of water in mine, but had just added new grain, and the next morning (and it was one of the recent warm mornings) the grain had absorbed the water to the point where it was exposed. I wouldn't expect it to start that much of a bacterial growth that quickly, but I haven't been able to find any other reason for whatever happened to my chickens. I know I also have something respiratory going around right now, but I figure that's just seasonal, because the two issues don't seem to be related and the respiratory is pretty low level. I would have guessed she choked on an object, but not that multiple birds would choke on an object in exactly the same way within a day of each other.
Right now they're on Tylan and being wormed. And getting treats. Lots of treats.