The Cal/Mg watering you plan to do in my opinion from what I see make sure this watering you allow for a good 'woosh' of runoff to come out the bottom and throw that away, test ph/ppm of incoming water vs runoff water will tell you a lot, if you have the tools. Those striped looking fan leaves with the veined blotchy look, that's Mg deficiency, but it may not be the whole story as a few things can cause a Mg deficiency and dumping Mg on them may not be curing the cause. Mg may be there enough but plant cannot access it for some reason and adding more while a problem still exists may just be adding burning salts in the mediium, which is my suspicion. Consistent overwatering and/or soggy medium and/or pH in medium being off can cause what you see, so if what I mention is in check and all you've been feeding is distilled, then go for it. Gotta be careful. Gotta be sure.
