So you are wanting to build up muscular endurance right? Like madcow said, you might want to take that 135 and lower the amount of reps in it. You can try doing some singles in the beginning of your workout at 135x3, 155x1, 185x1 and then try and get as many as you can out of the 200.
Like MC said, analyzing technique and where you fail is hard without posting a vid. Where does your form start to fail on the last rep of 185? Are you fast off the floor or are you having trouble at the top? What is giving out first is what I am asking? When you find that out you can start to build that weakness up with some localized endurance training for that muscle.
My lower back fails first on my lifts. I spend a certain amount of time doing the 45 degree hypers for reps on the days that I don't dead or after my dead training. I also do some static holds to help train my back to contract for my squat.
You just have to find the weak link and make it stronger. Maybe a training partner can help you analyze that aspect of it.