Looks like something's wrong with one of the chicks. :/
I thought the thing was lying to me because it happened yesterday, too, but after I messed with it for a little bit, it got right back up and started acting normal. That was almost 24 hours ago. It doesn't want to walk, and when it does it "penguins around" on its hocks. Its feed is medicated, but no shots. We bought it about a week ago now, so its almost two weeks old.
Its the biggest of the three I brought home so its not like it got picked on or anything. I felt its bones and didn't find anything unusual.
So far no others show signs.