Alright, so let me start off by saying, this isn't my first time around the block with chickens. I've hatched out and raised hundreds over the past few years, and aside from a case of failure to thrive here or there, or some other obvious malady like a birth defect, I've had tremendous success with them. Recently, though, I'm losing more chicks than I'm able to raise to adulthood, and the worst part is, there's no symptoms or warning. They have clean water, food, warmth, and a dry, clean brooder, but every morning I wake up to more dead chicks. There's no discharge from their eyes or nostrils, no paralysis or bloody stools... I can see no outward sign of illness before the chicks suddenly become lethargic and die. It also only seems to affect the smallest babies--once the chicks have most of their feathers, they are apparently no longer susceptible to whatever is killing them. Any ideas!?