Since it is dark now maybe try and pull eggs out and hold them to a light to see if there is anything inside and to see if there is a chick in there moving and possibly making noise.
When I used to let my hens hatch their own eggs they never had an egg under them that didn't hatch. Maybe the one that has already hatched is just a little early. If you are really concerned I would candle them.
When I used to let my hens hatch their own eggs they never had an egg under them that didn't hatch. Maybe the one that has already hatched is just a little early. If you are really concerned I would candle them.