I kinda think its your workout, on all of the workouts other than bench you are using the same weight on each set, I try to add weight on every set, I'd rather start lighter and get heavier than use a medium weight and do the same weight every set, also you said the last time that you could barely get that weight, and you might have been a little more in the zone the week before which could explain the difference. I know some days I do better than others.