Wow--those are good-sized air cells, I can't believe you can see them so clearly without candling!
Here is what I would do: Go ahead and candle in a dark room. If they are dead, they will be completely still and quiet in there. If they are living, you can look for several things: Movement at the membrane edge, where they are pushing against the membrane to the air cell; a shadow in the shape of a bill poking into the air cell and moving around a bit; the sound of cheeping or tapping inside the shell. Any of those signs and you have a living chick. If it is still and quiet, you probably have a dead chick, but there's a chance it's sleeping. I would put it back in the incubator for an hour, then check again. If it's still and quiet still, then I would start cracking it open, starting with a small hole over the air cell to look in and see what's going on.
Good luck. I hope they're okay--it's so hard to tell at this point without candling.