If the others are doing fine , that's good news. This one is probably still stressed from whatever happened to injure his foot which now seems to be better. Just give him some time, keep getting food in to him and he should hopefully start doing better.
Honestly I'd say he was being dominated in the enclosure with the other beardies, and his foot is due to a nip. It's very common for babies in the tank together at a pet store to suffer stress from the other larger, dominate beardies. They end up getting all the best food, best basking spots, etc. So you end up with a few larger, more active beardies, and a few smaller, more lethargic beardies with feet and tail nips. Very, very common, and the reason they shouldn't be housed together. You haven't had him that long, so he's dealing with normal relocation stress from his new home on top of the aftermath of being dominated the entire time he was at the store...Give him a week or two under proper lighting and temperatures, he'll be fine...
Update: my little guy passed away he wasn't eating the last 24-36 hours and I just got home to him dead. He was lying down but when I went to pick him up and he didn't move, I knew he was gone. But I have everything I need for the next one, and thanks to you guys I know some more stuff on caring for them.
Aw that's too bad, I'm really sorry. You tried your best to help the little one. I'm sure you'll make a good beardie parent when you get your next one.