Great news! I'd recommend water/vitamin treatment for the shaky chick, making sure they're warm and all that. Hope its legs can sort themselves out; do you know exactly what's wrong?
Give fluids, warmth, and wait. :hmm Sometimes things are wrong that we can't fix. Either way, you'll know soon enough. Sorry they aren't doing well. :hugs
Is it brown and shriveled looking? Could just be egg snot. Either way, don't try pulling it off his belly; if you have to get it off, detach it from the egg side.
Humidity's probably a bit high, but that's typically a good thing during hatch. If there's nothing wrong with the chick's legs, it...