You are dropping your butt too low and pushing the bar forward with your shins. This results in a non vertical bar path off the floor, which is why your pulls feel less than good. You may also be flexing your spine on the way up. Tough to tell from the video. Read the sticky at the top of this forum. Do the deadlifts steps verbatim. Stop dropping your butt as you squeeze your chest up.
Also, these weights are light for you. The bar is moving quickly. You must learn to embrace suffering on the pulls. You have an idea that they should be comfortable. When done correctly, deadlifts are very uncomfortable. You must get very tight and hold your back in hard extension on the way up. This feels bad. On the plus side, you only have to do 5 reps.