I am brand new to chickens and doing everything I can to do it right. We have 6 chicks about 2.5 weeks old. This afternoon I noticed one of them to be lathargec. It stands and walks and preens itself.....but it is not nearly as energized as the others....and it was a day ago. I have not seen her drink or eat...and her butt is clean. She closes her eyes and starts to fall asleep at every opportunity. Any thoughts? Thanks.