Hatching Serama Eggs

[GemGems]

We have two hens sitting on a set of eggs they laid themselves, one hen has been sitting on them 23 days today and the other is sitting on them a week, I'm not bothered if they hatch or not but I might aswell try and make the group a little bigger. We checked a few days ago and we discovered an empty shell outside the nest, but I don't want to try and move the mother to check if there is a chick underneath her and the rest of the eggs.

I would be grateful if I received an educated answer soon so I'm sure I'm not doing anything wrong
Thanks,