Duck egg behind others

[Sierra67]

I have 3 cayuga eggs in an incubator, temps have been correct and humidity is correct supposed to go into lockdown tomorrow but one egg appears to be behind, the 2 eggs are completely black with air cell in bottom as expected, this other egg is only half black with veins on the other half and air cell on bottom. What do I do, the duckling is moving inside but it’s behind the others

 

[Sierra67]

Someone please help

 

[FoodFreedomNow]

Can you post a candling pic of the egg? Sometimes an egg can look a little different (more "space" inside, for example) and still hatch normally.

Don't forget, hatching can occur 2 or even 3 days later than "hatch day", too.