Yellowing and Reddening of older fan leaves

You have clear mag issues. Try use epsom salt. It'll be a much better injection of mag for your plant. 200ppm added to your ambient tap ppm so if your tap is 100ppm make a batch that hits around 300ppm (tap included) And for soil. A PH of 6.5-6.7 should see you through your entire grow. Your growing in coco. So you should be hitting 5.8-6.3. PH. 5.8 been more optimal for coco. Good Growing.

Those crinkled damaged ends and edges look more like nutrient burn to me. She's clearly deficient in magnesium but I think your issue here is PH you say it is 6.2 which is at the upper end of "ok" for coco. I had this same issue on especially my grow "Nesia" early on. My problem was the PH was 6.2 and it was too high, the magnesium was locked out. So I dropped it to 5.8 and that solved all my problems. So I recommend going back to 1.25m/l or whatever the recommended dose for coco is of your particular cal mag - and drop the PH down to 5.8. I am not sure how accurately you are monitoring your PH but if you check the PH of the run off that is a good indication of the medium PH. I have found that it naturally creeps up over time, and in some cases I have had to flush the plant with PH water to get it back down to the right range.