As said above you should try a couple months with less volume but greater intensity. 30 second rests between sets. Super sets, drop sets, forced reps, rest pauses etc etc. keep the body guessing mate. Mix up your routine.
also try focusing on greater thickness as well. You will get wider as you get thicker. T bar rows, bent over barbell rows. Deadlifts(rackpulls) Row row row row row!!!! Don't focus too much on a number of rep count either just go by feel don't put a number in your mind because that is where you will subconsciously stop at. Push your body till it gives out on you. When most people give up its their mind that fails not their body. The army taught me that when you think your at your limit and your body is about to give way that you are not even close to failing. The body is a stubborn bastard it does not want to lift all that heavy weight so it makes you think that you have had enough thats where your mind must take over to show it that it is not even close to giving up
Hows your mind muscle with your back? I find its my hardest.
And don't forget the dumbbell pull over