What's up Pure !?
You rocks will stay moist as long as your bubbles are popping and misting close enough to get the bottom of the pots wet.
An inch or 2 between the top of the water and the bottom of your pots.
In the beginning, and until about 7 - 10 days AFTER the seeds sprout, I keep the pots submerged about an 1/2 inch to 1 inch IN the water/solution. They won't suffer or drown with adequate bubbles/air.
Second, get new nutes. Don't use those old ones.
Definitely get hydro nutes.
A lot of ppl use Pure Blend Pro, and reading the back labels it clearly says for soil or hydro soilless grows.
Soilless Hydro is things like Pro-Mix, Sunshine #4, Coco, Hydroton, Dyna-Roc, Rockwool, etc.
But I'd stay away from it all, except Hydroton and Dyna-Roc. The rest causes too much PH fluctuation IMHO. And no Pro-Mix or SunShine #4 in DWC obviously.
I have PBP for my soilless grows, but for my DWC I am using GH Micro and Bloom with PBP Cal/Mag and NOTHING more.
Check out my "12/12 from seed" grow. I started my first DWC this month too.
At DAY 11 and 29 today . Two diff strains going right now.