That is most likely not mold but salt buildup. As long as your plants are OK, don't worry about it. However it might be a sign you are overnuting your plants.
Usually white means a fungus rather than a mold. There a many good fungicides available at garden centers but fungus typically won't cause any problems with flowering plants. Reasons include that the fungus may only colonize the soil near the light, that the plants will probably finish before it becomes a problem and/or that many types of fungus are harmless or even beneficial in ways. Mother plants have a higher chance of problems from molds and fungi since they can stay in the same soil for a long time.
What if your seedling is only ten days old, and there is tiny grey mushrooms popping up around the plant? Can anyone please tell me what that may be and what needs to be done about it
Thank you for your imput
One luv
Lee