Don't touch that plug! Candle them - you'll know if they have died or have stopped developing. A cellphone flashlight is good as it's a very small, concentrated beam and they are usually pretty powerful - put the fat end of the egg against it to see what's going on. And a very dark room (nighttime) is best to candle in.
A full, dark egg with a big looking air cell means the chick is good and close to hatching. The air cell gets a bit of a tilt to it before they pip internally. If there's a slightly yellow, watery gap between the foetus and the air cell with no veins visible then the foetus has died. If there's still a little gap but you can see red veins then they are still a day or so away from hatching. You may even get a treat and see a little shadow beak in the air cell (chick has pipped internally) wondering where the bright light came from.

Do keep us updated.