help asap with duck eggs

[jollayhollay]

Hi. I have duck eggs that are forming what seems like cracks but aren't on the outter shell. They are on day 20 under a broody hen. (Chicken) we have been making sure they are turned so they don't stick as the hen also has chicken eggs. What do you guys think this is from? I may be able to upload a picture later.

 

[Amiga]

Photo's would be helpful, thanks. I am not a hatcher, but we have several on the Duck Forum. In fact, you may be able to get help over on this thread https://www.backyardchickens.com/t/850706/the-broody-duck-thread-for-2014