Looks like the ph buffers faded away, possibly getting rootbound, possibly a salt build-up, and how far are you keeping those 8 CFL's from the plant?

YTou might want to bump-up the ingoing ph to near 7.0, and see if that helps.
When you water, do you get a lot of runoff, or a little bit of runoff? (are you regularly getting water to the lower root zone?)
FF Grow Big and the Tiger Bloom can and will build-up salts over time. I do monthly flushes to wash these away. Tiz my only complaint about the Trio, but it's still my favorite nutrient line. Does the medium absorb water, or does it run right through?
I'd cut back on nurtrients a tad, as sativa dominates require less nutrients to begin with. I always cut the Big Bloom in half, regardless of strain.
When was the last transplant? Once rootball is fairly dry, carefully slip it out of the pot, (don't break anything) and see if it's rootbound.

Specifically, what kind of "commercial" mix are you in?