Can we get a full plant shot at all? I'm not sure i could diagnose septoria, or hunger, or natural shedding without seeing at least more of the plant. Tbh, that leaf looks like it went from a bit too much nitro, to now too little. The necrotic spots do look suspiciously round, but can be caused by literally millions of things. Septoria is very uncommon in a cannabis only garden. Best of luck, don't forget to bug me anytime and always more pictures as opposed to less. Whole plant, top, bottom leaves, node closeup are critical to diagnosis.