Im having more or less the same issue, also in a tank, with a 150 watt red light heat bulb hooked to a rheostat. I have a thermostat for the heat pad, with probe between pad and glass, a thermometer probe inside the hot hide another in the cool hide and an accurite thermometer/hygrometer sitting on the cool side of the tank to measure ambient air. My hot hide fluctuates from 88-92 with the thermostat kicking it on and off at a setting of 90. the cool hide sits at about 84-86 and my ambient usually reads about the same. My humidity is constantly dropping to about 35% because of the damn heat bulb. Id have to mist a few times a day to keep it around 50% and it has already caused a problem with her first shed. My solution is going to be to hook up a small humidifier with tube pushing the moisture into the tank. Ill likely have to put it on a timer as running it 24/7 would prob keep the humidity way too high. Im also switching to fine shredded coconut husk for a bedding as the word is that holds moisture way better than others and there is not the high mold risk like with aspen. If I were you I would consider those two options. humidifier is pretty cheap($30 or so) and the coconut bedding can be found for the same prices as aspen. I got mine on amazon just havent put it in the tank yet. Also the thermometers I have, Vivarium Electronics, the probes measure humidity and temperature. You may want to consider these so you can get accurate humidity readings in your hides themselves. they were not expensive($12 i think) from reptilebasics.com good luck