Nutrient issues or some other problem?

Looks like a fairly typical example of a calcium deficiency to me. Add/up your cal/mag dosage. The affected leaves won't recover, but it should prevent it from getting too much worse. Autos seem to be calcium hungry, especially if growing in coco coir.

could be a sign of phosphorus, potassium, magnesium, sulphur, manganese deficiency. But also fertilizer burning (stronger brown coloring) or heat stress (brown edges) possible. but to be more precise what it is. need to know more about your cultivation

Yeah... without a diary, mate, it's going to be really hard to give you advice on how to fix this... it looks to me like it's a phosphorus deficiency but WHY I can't tell you.... I'd check your pH, make sure it's between 6.2 and 6.5... Do start a diary... that way, when issues/problems/questions arise, we'll have all the information needed in order to give advice... it helps us help you! Good luck