If you raise the hygrometer off the substrate, the humidity will go down.
I always wonder about getting so particular about RH when a major contributor to the number on the meter is the location of the meter. Sitting on the substrate, it is going to read pretty high as long as the substrate is damp regardless of the RH of most of the air in the enclosure. (The wet wall behind it is certainly a factor too. Did you just mist, or is that condensation?) Lift the meter up and toward the vents and there could be an inch of water on the bottom of the enclosure and the meter would probably still read something thought to be OK for a BP.
Scale rot is caused by damp substrate (well, it is caused by bacteria or fungi, which are in turn encouraged by chronic wetness). RH is related to substrate moisture, but depends more on ventilation. If the substrate is just barely damp on the cool side and really close to dry on the warm side that's pretty good for a BP that's not in a shed cycle.
If the RH needs to be tweaked after the substrate is dialed in, then either modifying ventilation or (my favorite) using the water bowl as an evaporation pool works to increase RH (if the RH needs to go down, then move the bowl to the coolest part of the enclosure).
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