1of the 6 chicks we just got yesterday seems to have trouble walking and is less social than the others. She is super sweet & kind of vocal, too. She looks like she's panting a lot. She doesn't seem to be acclimating like the other chicks. It's like she doesn't have good balance. She's also smaller than the other 5, though they're all different kinds, so that might not make a difference. Thoughts? Suggestions? Could it be Marek's? I'm not sure if they were vaccinated before we got them-- from a feed store.