How do you know when you have a duck egg "quitter"?

[feather2]

I have duck eggs (on the 13th day of incubating) and they all have dark blobs and looks like some have air pocket on the sides. They don't seem to be moving at all. Do they get a blood ring this late or how do you tell if they are quitters? Thanks

 

[ChickenToes]

Do you see any veining?