They can go up to three days without eating or drinking as they are still absorbing their yolk, but the sooner they start to eat and drink, the better. Are they in a brooder or under their mama? If in a brooder, you can take your finger and "peck" at the food with it to try to show them what to do and keep dipping their beaks in water. If they're under their mama, I'd have food and water available and she'll show them what to do (usually). Are they active, moving around, etc?
Could it be possible they are eating and drinking without you actually seeing it?
They're in the brooder. It is possible they are in between checks. They're pretty active right now so I'm not to worried. I'm temped to bring in one of my older banty chicks who is about their size to show them what to do.