Leghorns not hatching

[Sophie4321]

I have eggs in the incubator
A mixture of mostly marans and leghorns and a few others
Most of the others have started hatching or have hatched but the leghorns havnt really done anything (1hatched 1 hatching out of 12) they are really big eggs and were all candeled at lockdown and were all alive then

Does any one know why this might be

 

[Sophie4321]

 

[Gray Farms]

Just keep them in there. Its not uncommon for chicks to hatch at as much as 25 days.