Inside duck egg looking brown

[packsr17]

Help! I’ve not incubated ducks before. Day 28 is today (Tuesday 4/15) if I counted correctly.
I have 2 eggs in incubator. The other has just made a small crack, but this one has been making cracks since Sunday. Now the membrane is looking like this, and this just doesn’t look normal to me.
Still chirping and active inside.

 

[casportpony]

Welcome to BYC. When did you set your eggs? March 18th?

 

[packsr17]

Welcome to BYC. When did you set your eggs? March 18th?

It was either the 18th or 19th.

 

[SilverBirds]

Looks like the membrane is starting to dry out. What is your humidity at?

 

[Yardmom]

If your membrane is dry, apply some food grade oil to it. A q-tip works well to put a thin layer.