Three days ago I bought two baby chicks. One of them is very weak. I have found her many times a sleep on her back. She is also very slow and doesn't move around too much. Although, she does eat and drink, just not as much as the other chick. Additionally, she will occasionally have diarrhea. Plus, she is very chubby! I checked and she does not have pasty butt. Does anyone know what's wrong with her and/or what I should do? Thank you all so much.