Nitrogen toxicity?

hi, my 3 plants are on begining of week 7 since i put them in dark each night. They grow outside in 3gallon fabric pots. 2 of them are lemon thsi kush from buds i bought in a dispensary. Cant find a lit on those strain. Since a week, leaf stem turning purple and some leaves too. Im in soil with own compost, using botanicare pbp bloom nutes and some dutch science fir bloom. Dutch science is 6-2-12.. with humates kelps and other mineral... they say to use for blooming period. Maybe 6 nitrogen is a lot in this phase? The plant looks ok even if i got some mites. But im wondering what causing that? Maybe strain relate?

Any thoughs?