mobile vs immobile -- where it is on the plant tells you this.. if it's sucking it from the bottom it's mobile. if it happens where light is most prominents, it's more likely immobile.
how the fade occurs from margins to tips or tips to margins is a differentiating factor too (when looking at leaf chart -- see one linked in my GD profile comments)
dots, colors of the dots, how it starts and progresses, etc.. all help you deduce what is going on.. this is only part of what you need to do to make a confident decision.
pH is important.. keep it consistent or adjust and keep it consistent after that.. this will impact the concentration and ratios of nutes needed to keep a plant healhty -- all 3 factors are relative to each other to some extent -- at least in the context of a range that produces a healthy plant.
so, you'll need to look at what you are feeding too. I have a spreadsheet that adds up ppms from the label %s -- handles %w/w too. US standards for p/k labeling.
An ECmeter will help determing if there's too much of everything, too.
Without all this information, you are blindly guessing -- might be right and that's awesome if true.. but cal-mag had magnesium. epsom salt has magnesium and sulft.. don't overdo it on the Mg or you will potentially lock out any number of cations (positive ions, like Ca or K or P, zn, fe, ...)
my point is., you may find you provide plenty of what you think it is, which would mean the problem will get worse- - potentially.. and anyone that's confident is just living in bliss without this information.