Make a mash from their starter crumbles and some sugar water. If baby isn't eating on its own- feed it through a medicine dropper. After the stress of being shipped, some need a little help. The sugar water mixture should put some food in its tummy and some pep in its step. Good luck!
If it's quiet and not moving around much, I agree with the sugar water: they get low blood sugar, and it knocks them for a loop. I'm also a big fan of "mush" made from chick starter crumble or mash, and water. If you scoop some up on a finger and say, "Chick chick chick!" then the chicks think you're Mommy showing them a treat, and they will peck at it. Sometimes it can take five minutes for the sugar water to kick in, so give the quiet one about 5 drops, wait a few minutes, then offer the rest some mush. Hopefully when the quiet one sees the rest getting all excited, it will want some too. A super boost for chicks is a small amount of hard-boiled egg yolk--maybe half the size of a pencil eraser, per bird. It doesn't take much, and it's packed with nutrients. They love it.
If it has diarrhea (pasty/dirty butt) then electrolytes are also a good idea, but generally if there is no diarrhea then electrolytes aren't essential. Good luck!