I had a similar issue just yesterday, and fixed it with a change in heating pad. Started out with a ZooMed ReptiTherm UTH plugged into a ZooMed ReptiTemp rheostat. On the lowest setting it was definitely hotter than I wanted. On our other tanks we used the ExoTerra HeatWave "Rainforest" UTH (which is cooler than their "Desert" model). Now on the lowest setting it is perfect.
Ian.