help! whitestringy stuff found on substrate surface

[newaquarist100]

Im attempting the dry start method with the mini leaf seeds for my aquarium and Its day 5 after seeding and I notice these white string-ish things growing from my plants. Is this mould? or the roots of the mini leaf clumped together? or anything harmful?

 

[ADsnail]

Looks like hair algae. Do you live in a humid environment? Even in a climate-controlled house the humidity is present and causes things to mold that normally wouldn't in drier climates.