Originally Posted by Socratic Monologue
Pulling out all the sphagnum on the substrate and replacing it with lots of leaf litter will help reduce the excess humidity a bit, and will give the frogs the choice between dry substrate (on the leaf litter) and wet substrate (under the leaf litter) that they need.
Improving the ventilation (ideally, with something you can vary according to season, temps, ambient humidity, amount of plant growth in the viv, etc) should be a priority as well.
This, along with the rest of the advice I'm this thread, is great advice.
I would remove the cholla wood now, it's unlikely to last well in your vivarium, and it's easier to remove our before the frogs are added than afterwards... ;-)