I have one sick 6 week old chick.?

Im not sure whats wrong, she sometimes lays down and closes her eyes, her body is all poofed up. I haven't seen her eat or drink anything. She's been like this since yesterday morning, she even says in the box while the other chicks go out into the pin. They have medicated food, and plenty of water, so im not sure whats wrong with her. They've all be vaccinated and just to make sure she's not contagious I brought her in the house. I dont think she's been pooping at all, at least i haven't seen any in the box that she's in by herself. I hope its not depression, we had 8 chicks but a couple weeks ago two raccoons snatched 3 of her sisters, but were raccoon free. o: I just don't know what to do and Im hoping she'll pull through it.