You still have some time to go man, 8 weeks is the general rule of thumb for flowering period, about 60 days total, but when you are getting to about day 45-50 you be the judge by how many of the hairs have turned brown, unless you go out and buy yourself a handheld microscope, then you can judge on when to harvest by looking at the trichomes themselves. I don't have a microscope yet, so I judge by the hairs, usually when about 10% of them are brown I go ahead and begin to flush, clean phed water, then when about 75% are brown I harvest.

I use baking soda as ph up and some stuff I found at lowes for ponds and stuff for ph down. I ph all my water to ~6(I'm using the GH ph solution drops) after mixing nutes.

hope this helps!