I think I'd be looking for the obvious first. What's the temp of the brooder? Heat lamp or heating pad? Is the entire brooder warm or is there a nice cool spot they can get to? Chicks don't do well when they overheat...they get quiet, lethargic, and can indeed die. I know that the books all say if the chicks are spread out with their wings spread and they are panting, they are too warm, and that's very true. But they don't always do that. Sometimes they just start to fade away when they are too hot. Conversely stressed out new chicks don't always give the accepted indicators that they are chilled, either, although that's more likely to be true. Are they piling up?
After you've made sure that they are safe temperature wise, then I think I'd pick up some Nutri-drench. It's the one "treatment" that I always have on hand since I'm not qualified to diagnose and administer meds to my chicks. Nutri-drench goes directly into the blood stream, bypassing the lengthier digestive-then-into-the-bloodstream route and can give stressed out and weak chicks a real boost, real fast. If that's not available then a little sugar water can help. Every chick that arrives here gets a dose of Nutri-drench first thing. I've still lost a couple of chicks if the stress was just too hard on them, but they may well have had underlying issues not apparent at hatch, and hatcheries sending out thousands of chicks a day don't always take the time time to look each one over before putting them into the boxes.
Good luck! Keep us posted. Most of us have lost chicks at one time or another, and no matter how long we've been at this we hate it as much the last time as we did the first!
