I'd change the location of the plants and get the mold out. It's most likely due to increased humidity from the plants. I had an outdoor aquarium in my last apartment, and the moisture caused mold in the corner next to it. My husband invited
mold remediation restoration san diego, and after that, we bought a closed aquarium. Although we had to spend money on it, there was no more mold in the apartment.
In your case, good ventilation may solve the problem, but I'm not sure about the dehumidifier. Then the air may become too dry, and the plants won't fit the microclimate.