Nute excess or deficiency??

cal mag and lower ph to 6.3

That looks more like Calcium than Nitrogen to me. Growing in soil, There is a few things you can use. You could try dolomite lime but that takes a while to break down. So maybe try a kelp meal or seaweed extract. Another method 1 teaspoon of powdered eggshells. 2 teaspoon of distilled malt vinegar. mix together fo 5 mins then let sit for 1 hour, strain then mix with the water to feed.

I find using anyones nutes at full strength/schedule, is detrimental to proper balance in flower, for most strains. Once you get nute burn in later flower, it is hard to get out of it. Since new leaves are generally around the bud area, your existing fan and sugar leaves will suffer the most. You should still get a good tasting harvest, but when to start back up with the nutes and what strength the nutes should be, is a moving target. I would stop feeding for 2 weeks, and see what your new growth looks like, then go with a diluted solution, after that. Only time will tell, what is burn, and what is just yellowing of mature leaves Good luck, and maybe someone smarter than me, can give you better advise.

If you are in week 6 of flower you will sometimes start to see your plants leaf go yellow. This is just the plant consuming its own nutrient which is fine. If they start to look withered then remove the leaf. Hope this helps

Probably too much nitrogen. Cut down on whichever nute has the most N in it. It could also be a calcium deficiency caused by too much phosphorus. So if your nutes don't have much N, cut back the P a little bit and make sure you have calmag.