It is said that you can't lift over 90% of 1RM for more than 3 weeks or your lifts will actually decrease. (Of course with more advanced atheletes it's even less time.) Your body wants to perform the way it practices.
If you lift that heavy, your body gets in the habit of moving weights slowly. You've effectively detrained your nervous system.
This is also why 5x5 works so well. 5RM is = 85% of 1RM. 85 is less than 90 so you can stick with 5x5 indefinitely without frying your nerves too bad.
DE training will help you break through sticking poi nts in your lefts.
My recommendation: continue to do 85% of 1rm. Do 5 sets of 5. Add 5 pounds every workout. Once you can't get the 5th rep. Starting doing a DE day once or twice a week.
Andrew Becker Scranton, Pa