Autopots 1 out of 4 plants showing sings of deficiency and tip burn any ideas.

Day 12 of flower. Last night I was feeding at 1.6ec just bumped that to 1.7ec (840ppm). Calimagic is at 250ppm(3ml/G) then 8ml of Canna A and 8ml of Canna B. Back left TK is showing signs of some sort of deficiency? Possibly magnesium? Not too sure. Has that lighter green splotching and is showing slightly burnt tips. Its the biggest plant in the tent. Aside from that I'd say things are running pretty smooth. Running at 5.8ph in the autopot trays. 79-80 degrees. 58rh-59rh 1.05 kpa leaf temp 75-77. 500ppfd. 50/50 canna coco and perlite. Any ideas Advice? Thanks dudes!