I don't have too much experience with hatching, yet (2x incubating, 1x broody), but thought I would share what I have seen. When my broody was sitting on 2 eggs, they both looked like they were developing at the same rate. The dark area kept growing in both, and they looked the same when candling. When I didn't have any pips by day 25, I opened them both up. In one, I found a fully formed chick with an almost fully absorbed yolk that died for some reason. In the other, I found a gooey mess, with the beginnings of a tiny embryo. The air pocket always looked pretty much the same to me, too. So, you could be fine, as far as your chicks go. Just keep going. BTW, if anyone is interested in seeing them, I always take pics when I have to break open an egg that doesn't hatch. I think it's interesting.