2nd Hydro Grow - Blue Cheese

My first grow was just bag seed. It came out pretty good for a first time. A few mistakes a long the way but I learned.

I bought 5 fem Barney's Blue Cheese seeds. My plan is to keep 2 out of the 4 for mothers for cloning. 4 out of the 5 cracked on the 18th and these pics are from the 21st so they are 3 days old in the pics. 1 stretched a lot. Right after I took these pics I bought 8 more bulbs

I am going to veg using CFL's, Daylight 65K and switch to 400 w HPS for flowering

It's a DWC setup

21 gallon rubbermaid
3 inch netpots with rockwool & hydroton
Using distilled water
Fox farm nutes
1 pretty big air pump, and 2 10 inch (I think ) air stones
Right now my PH is at 5.9
PPM - 400


Will post new pics this weekend

If someone can help me with this; yesterday morning when I checked my Ph it plummeted. i mean to like 1.5. I used PH up and checked after dinner and it was about 6.0-6.1. This morning I checked it again andonce again it was in the 1's?

What can cause this? My PPM is still 400. In my first grow I never had a problem with PH dropping, only going up. On my first grow I used a DIY aero/DWC. This one is a DWC/bubbleponics.

Ant suggestions would be much appreciated.

Will post new pics tomorrow

best of luck dude, treat those girls well and you'll have fat buds in no time