Help!!! what did i do wrong with the eggs

[Icravepoultry]

My duck eggs in the incubator havent grown since day 18 and have a small black dot in them. One egg looks purple on the outside, the other three are just white. I have hand turned them three times a day sometimes a couple hours off but near the time. I have two other eggs that i put in later. Why are the black dots not getting bigger?

 

[Icravepoultry]

Ps.
The eggs are on day 25

 

[Amiga]

Could you review your temperatures and humidity? I am not a hatcher - perhaps you can contact some through this thread https://www.backyardchickens.com/t/760871/call-ducks-finally-hatched/9400