I'm so sorry for what you're going through. Still, it IS very common to lose a few, or several, in each batch. I've read that the average hatch rate in small hobby-type incubators is between 50-70%. If your last 6 eggs never hatch, plus one DIS and one quitter, out of 27 total - 19 chicks surviving - makes your hatch rate at 70%. That's pretty darn GREAT whether you're a newbie or veteran!!!!!! Be proud of yourself!
This is the first time since I started two years ago that I've got everything to hatch. My most recent batch before this one, in a friend's incubator, a Miller Mfg Little Giant still-air with no turner (I did them by hand) - of 36 fertile eggs I set to incubate, I only had 26 hatch successfully. Lost three more shortly later to unknown causes.
It happens. It's typical. It's why chickens lay so many eggs to brood over, then only some or 'most' of them make it. Mother Nature plans extra eggs so that the species can still survive in spite of losses.
By the way, larger eggs take longer to hatch.
I'd still poke safety holes in those last 6 eggs, if you're brave enough (under plastic!). If not, then leave them be for another day.
An eggtopsy involves opening the egg to see what happened. I've done it with eggs I was sure would not hatch (day 24, no pips). I have a little brooder coop with a window that pivots up, so I could hold the egg behind the plexiglass and see through while I probed the egg open, just in case it exploded. (Had that happen ONCE, never again!
) I wore old clothes, long sleeves, latex gloves, face mask, goggles, and used an Xacto knife and a pair of tweezers. I was able to identify a couple of quitters about Day 16-18, one who had his head between legs instead of under its wing, and one who pipped on the wrong end and maybe drowned in its own fluid.
the kids are going to think it’s rigged 
