Make your stance a little wider. Reach back with your butt and lean over more. You are too upright now. Descend a little faster. Your reps there varied quite a bit from one another. One would be really slow and the subsequent one would be faster. Leaning over more will make it easier for you to utilize the hip musculature better and going a little faster on the descent (without relaxing) will also help you handle more weight. Lastly, make up your mind to really push against the bar. The weight is trying to win. Don't let it. Show gravity who is boss.