It’s the same issue I had a few weeks back 
and yes it’s on multiple fan leaves. I’ve since changed my soil recipe for new transplants but the Purple Kush was already transplanted in the old mix so hopefully the issue is the soil and it’s now rectified. The original post was agreed it was a Ca toxicity issue but I have since had people tell me it’s a Ca deficiency so I started to question the original diagnosis. Those plants in the original post are harvested but the damaged leaves pretty much kept getting dryer and more crispy all the way to the end. Because I started to think deficiency I sprayed WCA(water soluble calcium) this week and now it’s starting again maybe it’s not connected but maybe it is and the original diagnosis of Ca toxicity was correct. Never had calcium issues in over 25 years of growing so has me farked.
I’m growning outdoor in a natural 12/12 light cycle here in the tropics so I grow in small 3 gallon pots and flip them small for multiple harvests(about once a month) so that’s why she is small and also why I can’t afford to have too many damaged leaves, otherwise it takes over fast with not many leaves to spare.
Those inoculations sound like great ideas, supplies are limited where I live unfortunately so a fungal dominated compost extract is probably my best bet and maybe some LAB.
I wish it was contact burn…