Incandescent lights will dry the air out pretty quick, especially 3 of them. They also generate a lot of heat. I can't think of any reason why you would need 3 big lights and a heat pad. Make sure you are checking your temperatures correctly.
These snakes need belly heat, not air heat. The temperature right over the heatpad if what you should be measuring. Heatpads without thermostats / rheostats will easily break 100 degrees farenheit, so if you don't have a temperature controller, AND you are using 3 lights, there is something wrong.
As for humidity, the only time you need high humidity levels is during shed. Find a solution that works and stick with it. For some it is heavy misting repeatedly during the shed cycle. For others, covering the screen works fine.
Good luck.
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0.1 Ball Python
0.1 Okeetee Corn Snake
1.0 Leopard Gecko