Chicks absorb the yolk before they hatch, they just suck it into their abdomen. They can live on that for three days or more without eating or drinking. That's why they can be shipped in the mail. The incubating temperature is fine for them. I often do not take my chicks out for two or even three days after the first ones hatch.
What date and day of the week did you set them? There used to be a hatching calendar on this forum that was wrong but I haven't seen it for a few years. An egg does not have 24 hours worth of development the instant you put it in the incubator. It takes 24 hours for it to have a day's worth of development so you say "one" the day after you start it. An easy way to check your counting is the day of the week you set it is the day of the week the 21 days are up. If you set the eggs on a Monday the 21 days are up on a Monday.
Don't put too much faith in that 21 day thing though. It's really not unusual for eggs to hatch one or even two days early or late in an incubator or under a broody hen. There are several different things that can cause that. Incubating temperature is a big one, if the incubator is set a bit warm they can be early or cool and they can be late. But there are other things that can affect the hatch timing too. So don't be shocked or too worried if they are bit early or late.
Another thing. Sometimes my hatches are over and all the eggs that are going to hatch have finished within 24 hours or less of the first one hatching. Sometimes that drags out over two full 24 hour days or even longer. That can be in the incubator or under a broody hen. That's why the chicks absorb the yolk, so the early ones that hatch can wait on the later ones.
It's not that precise. It can be really frustrating, especially when they are a little late. I've been doing this for years and I still don't like it when they are late. But hard as it can sometimes be, patience is often your best friend during hatch.
Good luck on that hatch. We are pulling for you and the eggs.
