Help!!! Mold specks on rock wool

Humidity got up to 60 for a couple days, its back to around 40 now. There was a little mold on a couple leaves. I pruned all the mold off. No more mold has appeared on the plants. However, I have since noticed some dark specks of mold on the origenal rock wool. What should I be doing to make sure this doesn't negativly effect my crop? What should my humidity be at? What else can I do to prevent the mold? Is there anything short of buying a new dehumidifier that will lower the humidity? I would appreciate any advice that anyone could share. I am still kind of new at this. Thanks