4 sets for compound AND 4 sets for isolation exercises isn't the best idea. Try 4 sets for the big lifts, and 2 for the isolations. And what everyone else said .. train the legs.
Maybe you see no more results b/c you been following the same program for 5 years..you need a complete overhaul. Too many machines, too much volume. I dont think doing bis the day before back is to productive either. How old are you?