6.3-6.8, your lower value would be appropriate for a hydro operation, not soil.

As long as we are discussing it, what made you decide on 16 hours? Veg is typically done at 18 hours or even 24 hours and with experiments that I have done here, you do get more growth with the longer light cycle. Personally I like 18 hours of light, as it maximizes the available light, but still gives the roots time to grow during the dark periods.