I work in restoration. If you humidity is above 60%, you will have mold start to form. Since your plants are in a tent, and mold requires an organic surface to grow, then your plants are going to be that surface.
Humidity occurs from a water source. Most likely, when you water your plants, the water is evaporating and causing the humidity.
Do you have ventilation for your tent? A fan blowing in, and one blowing out?
If you dont solve your humidity problem you will get mold.