I brought home 9 barred rock chicks from Tractor Supply yesterday afternoon. One of my chicks is slightly smaller than the rest, lethargic, does not care to eat or drink. It did have a minor case of pasty butt, but it's vent has been clear since I cleaned it up last night. It has enough strength to stand if it's jostled or poked at by the others, but has just been laying under it's shelter. What do I do?