6 weeks in, you prob have another 4 to go with this sativa. your problem is easy. you state your ph was high but now back to 6. well that would do it. a high ph-over 6.2-6.5 in your setup would def. lead to nute lockouts. I see a lockout of a couple diff nutes like K, MG and maybe zinc to name a few.
Phosphorus gets locked out of Hydro and Soil less Mediums at ph levels of 6.0-8.5.
Potassium gets locked out of Hydro and Soil less Mediums at ph levels of 4.0-4.5, 6.0-6.5.
Zinc gets locked out of Hydro and Soil less Mediums at ph levels of 5.7-8.5
Being 6 weeks in you should be ok and I would reccomend the following.
drain your res and refill with 1/2 nutes -bloom formula and micro formula. You can pretty much stop the nitrogen feeding after another week or so. I would also add 1-2 tablespoons of epsom salts to correct the mg deficiency. You are going to have to make sure your nutes have all the essentials in them.
lower your ph to 5.7 and maintain it there. seriously. add an air stone to your res if not one already in there.
you should be fine than. they can look like this in your final 2 weeks when you flush, but appearing this way now will inhibit your flowering.