Looks like Calcium deficiency to me bc of the rust colored spots. Also whoever said you had heat/light stress was correct bc you have cupping (tacoing) leaves. Your plant is too close to the light. Itll get worse the longer it sits that close. Also when your lights are too close it magnifies any other deficiencies you have like the Calcium issue. It makes any problems you have even worse due to the stress already being caused by the lights being too close to the canopy.
Just move your lights a couple inches farther away from the plants. As far as the Calcium issue, I would definitely up the Cal-Mag to a full strength dose.
Unless of course your super close to harvest then theres really no point bc you'll be harvesting before the Calcium you give it would even really kick in
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