Appears to be, have you been staying on top of your ph? If I were you I'd do a flush, and get a cal/mag supplement. I did this when I came across my mag def and cleared it up. I do hydro, dunno if you would go about it different in soil.
Thanks, Turm and MrStickyScissors
I added cal/mag last watering and it didn't seem to help. Wondered about nute burn too. The other plant next to it looks fine. Although they are a few days different in age, so on a different watering schedule.
I added cal/mag the last time I watered. About a week ago. It looks a little worse on the leaves that were already affected, but shes growing good and the new leaves look good.
Did that appear shortly after a transplant? If so it just may be a little hit from the transplant. I would monitor new growth and watch the affected areas to see if it continues to spread.