That's interesting. I'll have to mark them and keep an eye on them. I've been much more hands off with hatching this year and it is going much better. My crazy Hovabator has not been keeping constant temps for me. It might be that my house is just too hot but I'm having to adjust it often through the day. So, I've been incubating in it and then setting the eggs for hatch in my Brinsea. My current Langshan hatch is winding down. Out of 13 eggs, I have 10 chicks, 1 that is zipping, and 2 that haven't pipped. It was day 21 last night so there is still a chance for the last 2. I'm very pleased with the Brinsea but I wish that it help more eggs!
I hope the last two hatch for you!