I've always been told 5.8, and when you look at the uptake graphs, you get the best balance of uptake of all the nutrients.

So for now, I emptied and refilled the res. I currently have about a 1/3 strength thrive alive solution, 1/8th strength foxfarm solution, and a little under half strength earth juice catalyst. Hopefully this will fix the problems, they probably are a bit young for even the half strength nutrient solutions. I'll try to remember to post pics in a couple days.