Runtz F1 Zam - First Organic Cultivation

This is not a magnesium deficiency, but a severe potassium deficiency. This is why adding cal/mag is not having any effect. Advanced magnesium deficiency will presen the opposite way, that is, the leaf parts closest to the leaf stem will be yellow, not the outer edges of the leaf turning yellow. Regardless, I would not foliar feed any cannabis plant, always apply any remedies via the roots. The last 2 pictures show slight damage caused by mechanical means (rubbing, bruising etc) and are not symptoms of any nutritional issues. Remember too, anything you add via the roots will take 10-14 days to show improvements in the new leaf growth, it won't happen overnight!

I don't think this warrants a foliar spray. I believe Mg is one of the ones that can traverse the stomata, fwiw. 100% magnesium sulftate or epsom salt with no odors or additives is totally fine to use as a readily avaialble source of Mg and S. Many packages will even say garden safe or something to that effect (walmart equate brand does). This could be an Mg issue.. interveinal chlorosis with spots.. It takes 30-35+ days from start of the problem inside the plant before you see visible symptoms. Your plant may not quite be old enough to show such advanced symptoms of Mg. would need some sort of expectation of your unique soil's contents and ratio of what you've fed so far to help deduce what is wrong. Too many unknowns and not enough info. Could be start of a k-def, but usualy see more damage around the tips in that case. Some trace elements are possible, but that woudl more likely be nute-lockout or pH issues. in a soilless/hydro context you maintain about 75-80 ppm of Mg in the substrate .. hard to translate to a soil context, though. Strongly suggest you learn how to feed through the roots rather than relying on a foliar spray.. just gunks things up and increases risk with standing water on leaves etc (not only that, but nutrient infused water)... also, stomata are for transpiration and that's how it gets CO2. Slowing that down at all is a big negative. If something extreme is happening and you need it ASAP, that's the only time i'd even consider it. So far, never had to apply a foliar spray for nute-related issues in (knocks on wood)

I think you should take some runoff readings. It sounds like a pH issue to me.