One thing to add to all the great advice you got, yea soaking wet rapid rooter type plugs are not going to work out well, so the pro mix idea is nice, but never soaking or too wet,
And the humidity dome is important to a point, if youve been going 7 days already,
You should see root soon, but im comfortable with 10 or even 14 days sometimes
Each strain and circumstance is different, like really different, some will pop in 4 or 5 days, some take longer,
MY main point is that if you can see your roots poping out, you should / must slowly remove the humidity dome....
Maybe 2 hrs a day increasing, to most of the day, that will signal the plant that you are not being its friend anymore in a comfy zone, and that she must start pumping out the roots on her own.....
Best bet, next time get a cimple clone tray and plastic holders, pop rapid rooters in tray , wait 4/5 days, mist frequently and remove the lid towards the end to encourage plant to enter the real world......
Really easy