I was told that it's possible an egg broke and one of the mommas pushed it out of the nest. Hatch day is Tuesday so it may be too early for a chick, but I will check. I was also told co brooding doesn't usually result in a happy ending. So I am a tad nervous now.
It is what it is at this point. I'll pray for the best outcome 
was worried about wax pencil or sharpie because the shell has to be breathable/semi permeable. I did candle a sampling of 3 eggs (too?) early on, saw blood ring in one. Noticed the eggs temp changes significantly when moving/checking them and the lamp feels too hot really fast, so I haven't messed with it again :/ New eggs are not fertilized. Just have to wait & see...