V G,

I have seen this on plants before (again pictures go miles),
and was told to not worry too much about it and that it was a type of saprophytic
fungus. The way I dealt with the mold with to mix up some H2O2 with water, then
spray it over the areas.

To my understanding it is only occurring because of the
moist substrate. May I ask if you are just growing in dirt or something else? I
would suggest looking at the substrate drainage and allowing it to dry a bit
more thoroughly.

Also, this question might be better off in http://forums.gardenweb.com/forums/hydro in the future.