Firstly, damn you for thinking reps four and five were grinders. All of your squats were really fast and I am mad at you for going from 185 to 320 so quickly and with such good bar speed. Life isn't fair. I blame my parents.
All kidding aside, those really were fast. You just had to work slightly harder on your last two reps. Your stance is probably a bit wide, although that is tough to say from here. Make sure your toes are out at 30 degrees, not almost straight ahead. Drive your knees out harder. That may clean up the hint of knees slide you have at the bottom. Strong work. I would not reset yet. You have more in the tank. Also, check the sticky. Rear oblique works better for form checks.