Benefic or malefic ?
-Root affected look whiter
-We don't use any organic nutrient, but black carpet used in our last soil-coco session.
H2O2 and/or water submersion look to "kill" it, but if it's a benefic "mold", we can let them alive
Those roots a good. They form when there is lots of oxyigen around them. They will dissipear as they absorb water which is why it looks like you "Kill" it when submersing them.
Mold will not be a bright white but more of a grey-white color. Here is a link on it. https://askgardening.com/root-hair-vs-mold/
Happy Growing