duck egg turning grey?!

[lace03]

i have 8 duck eggs incubating and today is day 30. 4 of the eggs hatched day 28/29 and the other 4 are still working on hatching but i’m a little concerned with one of them turning a grey color. it’s still alive and breaking shell away just like the others.. but i have no clue why the shells is changing color. any other time my eggs have changed to grey they died. does anyone know what may cause the greying of the shells while still being alive?

 

[nuthatched]

Is it like a bruise?

 

[lace03]

Is it like a bruise?

sorta like a bruise but it finally hatched about 30 mins ago and he seems a little mentally challenged unlike the others. im keeping a close eye on him now

 

[lace03]

Is it like a bruise?

okay so i’ve looked at him closer and am now realizing that one of his legs seem to be locked up right against his body. it will not use the leg and keeps getting flipped on it’s back.