Not sure since they all came from one nest? could it have been one that had been brooded and got over looked? I'd dif keep an close eye on it you don't want an explosion in your bator and contaminate the other eggs.I have a question, I actually got 16 egg from the lady yesterday, but when I candled them the dirtiest one was almost completely dark. I put it in the incubator even thou I didn't see any movement. It doesn't smell so I thought I would give it a few days to see if anything happens. What would be your call on this?? They came straight from the nest so I'm not sure on the age of this one?? All the other eggs were nice and clear and I placed them big end up in the incubator and hope for the best!! Let me know what you think......