There is pretty heavy foxtailing, and the upper sugar leaves are that loaded with nitrogen it borderline looks like it's going into reveg.
A flush would be in order if nitrogen toxicity is an issue. If your in Coco, check your pH, if it's off it will effect the nutrient uptake.
I had a plant that was showing nitrogen toxicity around 4 weeks into flower, and a flush with pH balanced until two gallons of runoff have settled, followed by a day to dry out, and another flush with pk only seemed to do the trick to get rid of the odd sugar leaf pattern, and lessen the foxtailing in new flower production from there on. I stopped Canna terra Flores a week afterwards and the darkness disappeared. Continued to use Cannazym, molasses spray as boost and a half does of pk instead of bloom nutes and it fixed the problem.