I've hatched several batches of chicks this year and for some reason, this hatch is really quiet. The four oldest chicks (keets actually-they're baby guineas) just lay around in the brooder, and aren't making happy chick noises. And the younger ones still in the bator just lay there peeping once in a long while (usually they're screaming in comparison). I'm treating these the exact same way as all the prior batches. What's wrong???