Can you post pics of the whole system, setup,
nutrients and roots? Even if we can't see the white clearly your talking about, they can still be very helpful. Also can you post a link to the type of nutrients your using, and tell us how much your using of them??? What water source are you using etc. etc.? Fungi can easily grow indoors as well. Spores are airborne, so anywhere there is air fungi can spread. What is the humidity level near the plants, and are they getting good air circulation?