Mold is an issue in a sub-tropical climate. So is rust. I'd add a dehumidifier, or force the roof air to run by adding an electric heater.
My RV is in Orlando, Fl at the moment. Within one month the air compressor hose had mold on it.
Regards, Don
My ride is a 28 foot Class C, 256 watts solar, 556 amp-hours of Telcom jars, 3000 watt Magnum hybrid inverter, Sola Basic Autoformer, Microair Easy Start.