First step would be to find out what your measurements are -- get yourself a good thermometer and hygrometer and measure your tank -- do not get those cheap analog ones that stick on the tank -- get a good digital read out one. Much easier to properly monitor what's going on.
Ditch the wrap and get some plexi-glass to cover the top of your tank it's a much more efficient way to maintain your heat and humidity.
Substrate - change to a higher moisture substrate like cypress or coco.
If you live at a high altitude, run you A/C or fans a lot or whatever -- this might well be affecting your tank humidity as well.
Humid hides work for some people - may be worth giving a try.
In the long run there are a lot of people that keep their balls at low humidities without issue. Tweak your tank to see what works best for your situation.
Good luck.
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