If you stopped training arms and they grew...they are getting too much secondary work...or are the primary movers in your bigger exercises.
For back, I would concentrate on FEELING the muscle being worked...it usually takes a lighter weight and higher reps. Once you start to feel what it is like to actually pull with the back, you can start adding weight.
You may need to use different angles than traditional exercises use.
Point is...you really need to feel it working the back...and make that body part a priority for a while.
just my .02