Heat stress

Unfortunately I accidentally selected the spam reply as best answer. I was down with covid 2 weeks and could not do my daily checks for many days. What I surmise happened is that my feed was too strong and during the heatwave the plants stopped the usual uptake of water. But I kept watering/ feeding every day the usual amount, and the buildup burned them. The one on the end was sun exposed (on pot/roots) so git baked more than the others. That's my best guess. Got an EC meter now, flushed again. Git my levels down now. Resuming about 50% feed strength.

Cannabis plants don’t burn under the sun until it has plenty enough water. In the Moroccan desert it grows in extremely high temperatures. From what I can see, that plant suffered from a Nitrogen excess and too many nutrients. Stay below 1200ppm on your feedings and check the drain from the pots.

I'd say you are being vigilant so just carry on and ride it out. Not much else you can do really. Just be certain that's what the issue is