I found one of our almost 3 week old chicks lethargic and with eyes closed yesterday morning. None of the other chicks in the brooder show any signs of trouble. We separated and after a day it has improved. Eyes are open and it is drinking. I don't know whether it is eating. It moves around tentatively but is shaky. It is pooping. I'm no expert in chick poop, but the poop seems normal, perhaps a but watery. I didn't find any external injury. Any idea what may be the problem?