I can't tell much in the picture but if it's just fuzzy white mold growing ontop moist soil, I see that everytime I cook a batch of organics. Just living soil. I don't think it's harmful to the plants. If I pull up the mulch on some you can see the fuzzy stuff on the roots.
....hmmm, white mycelial strands-- pretty generic I'm afraid, so I can't say with any certainty that it's bad fungals; WPM usually only shows when it's cool, constant damp/high RH, and poor air circ', which I believe you are 0/3 on! 