You have checked and are sure that this mold is something that should be killed off? Many growers will see something like mycelium and think it is bad when it actually is a necessary part of the healthy soil. Mycelium and many molds are breaking down organic materials in the soil and the result is naturally occurring nutrients that are easier for the plant to absorb.
And after you've sprayed it off, figure out why it happened and fix that. Probably as simple as adding or readjusting a fan, but you might need to remove a leaf or two so air can get to the soil.