How to know if it died or needs help hatching?

[ComradeQuedtions]

All 12 of my eggs in the incubator looked to be good in the last candling just before lockdown and 9/12 hatched on first day of lockdown and day 21 was yesterday. Should I be concerned about the remaining 3 should I have checked again? Or do I just wait longer?

 

[New duck mommy 2021]

All 12 of my eggs in the incubator looked to be good in the last candling just before lockdown and 9/12 hatched on first day of lockdown and day 21 was yesterday. Should I be concerned about the remaining 3 should I have checked again? Or do I just wait longer?

As long as there is no external pip it’s safe to candle them
If they were my eggs o would check them
Although I don’t pick them up
I candle in place in case baby is alive in in hatching position
Don’t want to mix them up