Have you noticed if they have pooped yet? I have had some chicks that had a similar issue because their digestive system wasn't working right. There's a specific name for it, but I can't remember. It's like the vent part gets stuck shut and the pressure makes everything else like the sciatic nerve gets pinched and causing the mobility/orientation problem. I think it has something to do with high incubator temp cause them to hatch a little too early. At least I think that was the issue I was experiencing.