Egg yolks bad? Greenish casing.

[MinnPeeps]

I'm not a duck or aquatic expert at all. I'm not sure where you live. But does your area experience algae blooms of some kind?

 

[Stipenvlerk]

https://www.adelaidechickensittingservice.com/blog/what-causes-brown-or-green-duck-egg-yolks

Did you follow the link @Jenbirdee shared? It says the colour can be because of your ducks eating Acorns. Are there Acorns on your property?

 

[Cass8710]

I missed it! I do think it's acorns! I still don't want yo eat them though