If you don't have a thermostat for your UTH, it might be too hot (they can easily get up to 130 degrees which is enough to burn & even kill a snake) do your thermometers have probes? and if so is a probe directly over the UTH?
I do have a thermostat for my uth with the probe directly against the glass floor.
1.0 ball python--normal-"Anicho"
0.1 carpet python--diamond x jungle--"Evangeline"
1.0 feline--Siberian Forest Cat--"Zorak"
1.0 feline--American Short Hair--"Nimbus"
1.0 human--Italian American--"Josh"