First time hatching... We have 11 mallard ducklings. So far 10 have hatched (started around 7am, ended around 2pm). The last egg had internally pipped (and was moving), but not externally. I made a "safety hole" in the air sac end since it had been 18hrs since the other eggs had pipped externally, but so far nothing has happened (5hours have passed). Do I leave the egg sit a while longer? And should I leave my other ducklings in the incubator until the last one hatches? I'm worried opening the incubator will cause trouble for the last egg. Temp is at 100, and 75% humidity. It has only been 8 hours since the last egg hatched.