Is this a cal mag issue?

I am on week 5 of veg in 4 inch rockwool cubes following the drain to waste feed schedule using current culture nutrients, with .5ML of power.si per gallon. I am repeating week 4 as recommended by the company and I am noticing leaf/stem issues that I believe is magnesium deficiency.
I am feeding 1.2EC / 5.9PH but the run off is 2.8EC / 8.4PH.
75-82 day temp 70-75 night temp, 55% RH
HLG 600R LED light 24 inches from top of canopy

Almost all manufacturer recs for nutrient usage is to high
That looks like what has happened here
New growth will recover
I would run half rec dose from now on

To answer your thread title question..........No.

MickFoster said:

To answer your thread title question..........No.

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Do you have any tips to help solve the issue?