My guess is at some point the sun hits your window and focus's the energy almost like a lens and it's roasting that side of the plant.. Why it seems to be only on that one side.. do you rotate the plant daily? If not this might help.. 👊
When mine looked like that it was wind burn and from misting the leaves during day lights, check make sure ur fan isn't blowing right on ur plant I point mine at the walls, I'm a 1st timer but that was what happened w me. Good luck keep growing