at first glance, overwatering is my instinct, but could also be the other way, where it got too dried out in this heat.
to be sure would have to see it in person to inspect for bugs/spider mites and to check the pot/soil mix also to question about watering and fertilizer use, to see what the light is like, etc.
Might be a survivor of severe wilting ... It's in a pot, do you suppose that it was moved from near total shade out into the sun? So, sunscald?
I wouldn't expect right off so much dead tissue from spider mites. (Thought about writing "necrotic tissue," pretending that I have some specialized knowledge of plant disease ...
My first thought was herbicide damage! It looks like it might recover.