How to bring up lagging body parts.
A very simple effective way to bring up a lagging body part in terms of muscular development is add more frequency.
For example in my case i have lagging upper chest and lats so one day of the week i do a small simple workout
Incline BB Press
One arm BB Row
Add an extra 3-5 sets between the 6-12 range.
Simple give it try.
You cannot be physically strong if you are mentally weak.