Yes, that just happened to me for the first time ever. Didn't see mold till they'd eaten most of the bag. Lost two hens to that problem when their crops ceased to function.
Haven't read the entire thread, but that many acting that way and the liquid draining out makes me wonder if you got some moldy feed. That will kill a bird very quickly, pretty much kills the crop function. Do the crops feel "doughy"? Empty? Hard? Gassy?