White (mold?) substance on top of medium. Halp.

Growing in Pure coco
I think I over watered ( today the leafs are turning up, maybe you can see in the pictures below ), been watering after 2 days. Going to switch to every three days. But my main concern is that I found white (mold?) on top of the soil. The humidity has gone up to 60-65% I'm guessing that is the problem. I plan to build a DIY dehumidifier with two 2L soda bottles and rock salt as I don't have enough space in my tent for an electric dehumidifier. Has anyone tried this DIY method before or is there a better one I can use?

The plants look healthy, I don't see an issue. If the white substance on the soil is a fungus you can use a hydrogen peroxide solution as a fungicide.

The mold usually is not harmful.