Is it Septoria or something else?

wanted to say Mg/Ca take a very long time to present themseslves. If it is the cause, it was present weeks before you see first symptom. I'd still lock down other options before juicing ppm of either. 80ppm Mg / 100ppm Ca works for me, but i have hard water. So, if your water quality i higher or using low ppm RO, you will need more than that. Epsom salt is easy way to add Mg, but also adds S. You are in soil, so translate what you can from my soilless perspective. Think eggshells work for Ca? Then, you always have a calmag product.... lol. If a brand of nutes require more than a rare supplement for an odd plant, i'd consider a different brand.

Doesn't look like disease to me. Got the claw going and some other stuff, so it is a bit overfed. Lockout is more likely causing calcium and magnesiu deficiencies. helps to ask quetion from the diary this is about. Often times if one isn't listed, ppl skip the question, too. after looking quickly, i see you are in late flower. This could also just be senescence. You buds do not seem to mind, so it couldn't be "too overfed." A lil less p or k might avoid it... pH plays a role, of course, but assuming that is locked down. a little better ratio likely see less asymmetrical growth on leaves too, if not some genetic trait.