I would suggest to put your frog in a "quarantine" tank and leave your tank to settle. There will always be mold problems in a new terrarium. If you see that mold does not disappear I will to invest in springtails or isopods. And let only a few running in the viv as they will reproduce.

Can I know what type of wood are you using? I suggest using cork, driftwood, mopani etc.