You should probably cut back on the water. Make sure that the roots aren't submerged in any water too. If you can, pick up some HydroGuard and add it to the water. It really protects the roots from everything.
I've been growing the Nuska for about a year now. I love it. I was a first time grower with an aeroponic set up and had no problems with the plant. I did have a root rot problem, but that was due to drainage in the aero system. The plants grow fast and cloning is a snap. Smoke-wise it is...