IMO, if it were light burn, the top of the canopy would/should be the only part affected. But this appears to be on some of the lower leaves, as well.
I don't believe it's nute burn, either. With it showing as pronounced as it is, it would be all over your entire plant. Just my opinion.
Dr. Who was probably on target with the watering suggestion, and the potential for the umbrella effect with smart pots. If your soil doesn't get thoroughly watered, it develops dry pockets that will let the roots die. If this were to happen often, and in different areas of the pot, well...
Here's a couple more places to look for help with sick plants-
http://www.growweedeasy.com/marijuana-symptoms-pictures
https://www.icmag.com/ic/showthread.php?t=11688
They give a lot of specific information on the conditions that can cause lockouts.