Two were cheeping but only one hatched...

Yesterday it all began at about 1pm. We heard cheeping from one egg, then it pipped and later zipped around the egg. While zipping another egg began peeping. This seemed right because out of 7 incubated eggs (this was our first casual attempt) 4 of the eggs weren't optimally stored and they were two weeks old upon going in the incubator. The other 3 eggs were fresh from the hen's butt.

Just before lockdown two candled developed, five were not showing anything.

These went in the incubator on 7/21 and temps have been on the low side the whole time they've been cooking so I know it could take longer for hatching... I'm wondering how long I leave the chick in there with the eggs? When should I throw in the towel on the other egg that cheeped and is not pipping? Should I candle it?