First Grow! DWC & 600w vs 2 Atomic Northern Lights and 2 Chem 4 x SFV OG clones

I'm very excited to share with you all my first official grow. I've tried a few times when I was younger and each time never panned out too well for me. I finally moved into a legit place to do it and saved up the money necessary to build the setup I always planned. So lets get to it, shall we?

The supplies:
Cab is 5' x 4' x 5' and made of 2x4s and plywood, sealed and lined with mylar.
Light is an Ipower 600w dimmable hps/mh with XL air cooled hood
6" Ipower ~450cfm inline fan
Voltage regulator to slow the speed of the fan
Passive Intake
Medium is DWC in (4) single 5 gal buckets
SCRog down the road!
Air pump is a GH dual diaphram pump with 4 outputs
1 heavy 2" round air stone per bucket
We're using SuperNatural Nutrients

We got 4 clones from a local dispensary, 2 of which are Atomic Northern Lights and the other 2 ChemDog 4 x San Fernando Valley OG. The ANL girls were smaller cuttings with only 3-4 nodes and the Chem x SFV were a little larger with 5-6 nodes. All clones were in rockwool cubes with healthy looking roots within the cube, but none sticking out.

I picked up these babies 5 days ago and they've shown little to no growth. I'm assuming that's how it goes in this very early stage, but I'm getting impatient waiting for those roots to poke through the net pots! Currently, the water level comes up to the grow rocks and the air bubbles pop right on the rockwool. I added a tiny amount of ultimate thrive to the water to warm them up to their future meals. The current conditions are as follows:

Air temp: 70
Humidity: 57%
Water temp: 65
PPM: 225
pH: 7.9
Light schedule is 20/4

I've read mixed things about the relevancy of pH at such an early stage, so is it a problem? Should I add pH down? Any other advice about the conditions?