Moldy rotten egg.

[Bogertophis]

Update, the very moldy egg and the little bit of moldy egg attached to it are still moldy.
All the other eggs are fine so far.
So it looks as Deb said.

The mold is at the top, and not the bottom where it sits in vermiculite. I believe it was condensation dripping from the plastic wrap.

I removed the wrap on the 4 clutches and just put back the snap close lid, as the Saran wrap can sag if not careful!

2 out of 27 is acceptable, I suppose.

In my humble experience with snake eggs, it's too moist if condensation is dripping from the plastic wrap...although I also had several pin-holes in the plastic wrap.
Did you do that (make pin holes in plastic) as well? or not? While I agree that you never want drips of water onto eggs (they can drown), it's by no means the only
reason that eggs get moldy...some just aren't viable & they go bad, with or without water drips. When I had condensation like that, I opened it up for a bit (I lived
in the desert then, it was easy to get rid of "humidity") and then recovered them after some time (maybe a day?)...that helped, & the eggs later hatched.

All the best with your eggs...