I had one weak chick and I gave her gro-gel and it helped a lot. I gave them gro-gel the first couple days after shipping in a separate bowl from their food. I also put electrolytes in their water. She did end up having the same energy and activities but That chick didn't catch up in size until about 6 weeks. Her name is peanut because shes just a little peanut (I'm a dork). Any way tractor supply has save-a-chick I have never used it but a lot of people said it helps in other discussions like this. I would also watch her and make sure shes drinking and eating. Maybe she didn't figure out how to drink or something. Good luck.
Feed hardboiled egg mashed up (or microwave it and mash it). We had the same and am convinced it got ours going. I had written it off, but we continued to baby it and it is doing well.