Hello my friend, they all tell you what deficiency it is but not how to solve it... I would do a bucket clean. Get the nutrient solution out and lower your nutrients both from 1.5ml per liter to 1ml per liter and do the same for your cal-mag bring this one down from 2ml per liter to 1ml per liter. Lower your pH just a bit around 5.8 is better. Next to that you do everything right and I hope that this big bud will provide you with big buds!
This is classic nitrogen toxicity, the plant is being over-feed, especially nitrogen, you're giving it too much nitrogen during flower. It's not your ph.