Some eggs just don't make it for a variety of reasons. I had a whole first clutch just mold over and wither up. And a second clutch where one egg went moldy and none of the others ever did. I've had one from a first clutch show veins when candled and when everyone else was pipping, hatched, and out it was still plump and good looking. Upon opening the egg up, found a little blip of what used to be an embryo and veins. Each clutch is different.
Have you ever tried to candle them to see if they're showing signs of life? By this point you should be able to see veins and when gently pressed towards the 'dark spot' you should see the hatchling move within. Gentle handling doesn't seem to do any ill effect towards the developing hatchlings. That way you could definitively see which ones are alive and not waste your time treating an egg that has nothing within.
Listerine did save one egg for me this year, so I know that works. The egg was black, blech. So you're free to try whatever method you will. Let us know what you find out and if any do make it.
:-offtopic
I tried incubating leopard gecko eggs in perlite a few years ago, and experienced nothing but trouble. Perlite incubations were always too moist for me. I guess because it feels more dry to the touch than the other mediums and I'd add too much water.
Then I tried vermiculite when I first started with corn eggs, which didn't work out too well either. It was either too dry or too wet, plus it made a collossal mess everywhere.
So I switched to long-fiber sphagnum moss, and haven't gone back since. Its moist, but not soggy wet and doesn't cling all over the eggs. So you can cover them in a nice little happy pocket. You just have to make sure you get good quality stuff, usually from New Zealand without fertilizers added. And pick out the leaves and grass pieces that sometimes are in there, as some have a tendency to mold. But 2 years now and I'm still happy. Plus, moss has an antifungal property to it due to the tannins.
But after my crappy incubation this year I ran out of moss, so I had to use Bed-a-Beast. Barely moist, fluffed up in my typical delicup and the eggs are clean, turgid, haven't needed a spritz or a dry out and still waiting to hatch.
So before you have your sights set on anything this previous year, I'd try various things to see which you liked before doing all of your eggs like that. Maybe one clutch for each different medium, and keep notes of their progress. Something about not putting all of your eggs into one basket.
