I would leave the dome on until it looks like they have that first set of leaves established.
I have left the dome and heat-mat on but my temp rises to 85-90deg!
If i take the dome off the temp go down to 80deg but the humidity drops to 20%. Is the heat mat that really important at this point in my stage of growing? Maybe im over thinking about it, i allways do, maybe i should just leave it alone and stick to one way of doing it.
You should keep the roots warm w the heat matt and this will help keep the humidity up in the dome. If you could get some pics up that would help.
Here are a few pics of my lil bitches at 5 days from germinating
