you have a tall tank and aspen bedding nether are good for holding humidity.
these are some suggestions you could make to hopefully help IMO
you can add moss to the substrate, change to coconut husk or cypress mulch, get a smaller (shorter) tank.
Adding plants could help hold in the humidity as well.
A thick towel on the top of the tank dose the trick for me
It would be best to keep the humidity 55-75% all the time.