I'm going to second the opinion of switching to dirt. It is possible that the orange white's tree frogs need a slightly higher humidity than regular white's, so switching to dirt might help. I would also add a real plant or two to help with humidity - mine have a ficus tree. Froggie spends all his time sitting under it, and Chance hangs off the window below the vine. Froggie loves his ficus, so I'm betting your slightly dry one would love having a plant to sit under.