Maybe the show boxes don't vent enough?
I know that with 6qt tubs if you use too big of a water bowl they can easily fog over.
I've just started assembling mine this weekend since I have numerous clutches coming, it used to be a china hutch

It will hold 35 hatchlings in their own 6qt tubs, I'll be making another one across the room since I'll need more like 60 spaces

4 inch flexwatt running down the back of each shelf and with lids they keep the humidity up very well. Tubs with lids is a bit more of a hassle than a standard rack with lidless tubs but in a pinch this way works very well.
A hatchling rack will be nice, "someday" lol, but for now this will work just fine.
It's similar to how I kept my hatchlings last season but on a larger scale.
I was very happy with how well my last years snakes grew right out of their 6qt tubs in no time at all