mold on eggs?

[mpkds]

I have 8 eggs in a hovabator, 1 egg from the 1st clutch (laid on May 10th) has yellow stuff on top, I cleaned it off with vinegar and water (read this in a forum) but it came back. The same thing is on an egg from her second clutch (May 27th). I have seperated these from what looks to be the good egg but am not sure if this is mold or not and I can't seem to find a picture of mold on eggs anywhere. The eggs that seem to be bad are not growing the same way the "good" eggs are. Should I get rid of them? They are not dented, just a little yellow.