Is the plant looking droopy?
I would take out some of those pebbles or try to figure out how to keep the top layer drier around the base of the stem. I like to leave my rooting plug showing above the level of the HT. You'll want to stake it. If it looks even slightly mushy, get going on Serenade RIGHT AWAY- spray it on the surface of the medium to combat or prevent root/stem rot.
You are also seeing white bumps- those are the nubs of adventitious roots, which grow in very high humidity conditions. They aren't bad, but signal that you have a lot of moisture in that region. More fans, if you can, even just small ones placed in among the plants to move air.

The rootbound thing is another issue entirely. There's a whole bunch about it in one of Weedhound's DWC logs.