mold yes or no? with pics

is this mold yes or no? Im useing rockwool i had them in hydroton but timer is f***ing up so never know when feeding so i took them out and this was on top of some of the rockwool is their any way to kill it if it is old with out hurting the seedlings

I don't know ,put a few drops of hydrogen peroxide per liter of water,and spray it.rockwool should be covered

yea im getting to that

bump........

Yea, it's mold, but it might not be that bad. I only grow in soil, and I get that on my clones EVERYTIME on the outside of the peet cup. I do nothing about it. Moisture obviously causes it, but it never got onto the plant nor ever caused issues. I would try putting a fan on it if it's causing you stress, otherwise, leave it and see if it does anything. If it kills your baby, you know to do something about it on the next one. Good luck!