ok i'm no deadlifting expert but watching that video, there is hardly any leg movement at all happening, especially during the last few reps. they almost start to look like a modified good morning type movement instead of a deadlift. your butt is barely lowering at all when you're puttng the weight back down and instead you're bending over to compensate for that. the angle of your torso when you started your first and last rep was pretty good but in between it got increasingly to the point of being almost parallel to the floor which if i'm not mistaken puts your hips at a serious disadvantage and makes your lower back take the brunt of the work to do the lift. a thing that helped me out when deadlifting was to think of the movement like a spring. when a spring gets compressed, it all gets compressed equally and when it gets released it releases equally, all coils moving at once. i would say not to increase the weight anymore until you get these form issues taken care of or you could be at risk for serious lower back injury.

i used to train at a place that had those hex plates, man i sure hated them for exercises like deads and rows! Of course the entire time i trained there i NEVER saw anyone else do deads or rows anyway, lol!

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