I re-did both tanks this morning, and put stryofoam (spell?) insulation on the bottom. Because the hatchlings are so small (23 and 21 grams, and about 13 1/2 inches long), I used a big hide to cover the whole heat pad area, and put a tiny hide inside. I took the thermometer probe off the floor, and now have is just a bit elevated inside the large hide, in order to get an ambient temp in there.
The temp gun has never measured anything over 90 directly on the glass (88 on paper substrate), and the snake has the option of laying on the top of the smaller hide within the warmer ambient temps (low 80's) of the big hide. My tanks are set-ups are identical. Will be checking frequently with the gun.
They are always active at night, and frequently during the day, but both have refused their last two meals, and I think that might have been because of the fluctuations.