What is the tanks humidity level during the day when lights are running on the tank?

Is there a drainage layer below the top layer to allow for proper drainage and the moss to not sit saturated?

Molding in a normal process for the tank cycling, and should go away over time. Does your tank have enough accents to keep the frog off the bottom of the tank so that it doesn't have to step or move thru the mold?

Post a pic, it may help others reply with some helpful ideas.