Is This Mold!???

Is This Mold!??? I had the humidity dome on for 2 days with vents open, seeds barley popping soil today. Should I take off the dome completely or harden it off and tmr take it fully off? Right now I have it half on

Not sure what that is but your medium is too wet and there are reasons why domes are only for clones and sports arenas

Looks like mycelium from the pic. If your growing in organic soil, this is usually a good sign. I do things to promote it on my notill beds.