Here's hoping that some people are still online, because I'm no expert on chick diseases.
@azygous
@Eggcessive
@WVduckchick
@oldhenlikesdogs
In the meantime, can you post pictures of the chick? How about pictures of the poop? (A surprisingly large amount of people on here want to see pictures of poop.)
Generally, there are a few things recommended when the chicks are sick.
Electrolytes. Honey in water is good, but if you add baking soda and salt as well, it helps the chick retain the fluids it drinks instead of their just passing through. Recipe is:
2 tbsps corn syrup or sugar (I imagine you can use honey as well)
1tsp baking soda
1 pinch salt
2 quarts of water.
I think we can rule out a temperature problem, as no one else is sick, but
vitamin deficiencies tend to affect a small percentage of the flock, even when the entire flock has them. Can you get a hold of poultry vitamins or poly-vi-sol (low iron) for babies? Vitamin B-complex tablets ground up and added to the water can also be helpful.
Coccidiosis is another really common problem in baby chicks. It happens when chicks are exposed to too much soiled bedding or poop for too long, especially under stressful conditions, such as while they're being shipped.
The article says that the poop of the affected is bloody, but that's not actually always the case, so don't rule it out just because there's no blood. If you're feeding medicated feed, your chicks probably don't have it, but it's a preventative rather than a cure. If your chicks do have it, you need to treat it with Corid.
Good luck. Sorry for the book and welcome to BYC.