You have no diary. Very hard to make a call without more facts, and plant history. Have you had leaf degradation. Are them parts of the leafs crispy?Cause I can also see it on the sides or am I wrong?, if I'm right, without knowing nute strength, flush and that, but again I'm guessing, but my guess is nitrogen tox. More details and I'll be able to make a better judgement or someone else might be able to pull a rabbit out their hat, cause that issue without seeing earlier signs could be a number of things. I'm not going to list because that won't help you in the slightest. Best of luck.
Sry 1st message had to fix awful grammar, am high lol.