I had the same problem when i was living in Florida (can You imagine??) and my Ball like higher humidity... i can't get perfect shed in H less that 70%!!!!
This was the steps.setup was 20g tank with screen zoo-med heat pat on one side and red bulb on the other ....
I switch bedding from aspen to reptibark...I put large surface water dish... I think that was XL exo-terra and i go to my neighborhood glass store and order cover from Plexiglas covering around 60% of screen,
That was like magic... Humidity bump to 65-70% little misting before shedding, regular feeding And i had great healthy ball python....

hope that helps