Confirm what kind of Deficiency

Now then,it still could be Calcium.How long have you been adding Cal-Mag it could take more than a week,and is it only on the older leaves.Big difference between old and new leaves.The old leaves may stay with the damage but as long as its stopped and hasn't moved up the plant or got any worse then I'd say it was Calcium.Potassium deficiency doesn't look that different but the patches are dark brown instead of rusty like these.