Hi Steve, back day consists of a few sets of alternating grip pull ups, dumbbell rows - usually overhand. Since I posted this, I did have a look on YouTube and learned that underhand rows hit the lower lat
Try arching the back forward first (just a little) and contract as you pull then arch backwards (again just a little) and you'll see the backwards arch gives you a better contraction.
Use different handles and bars. I switched up low cable rows a little while ago to a wider handle.
Pull into the body low, middle then high.
Finally, really squeeze the bar or handles as you pull / row in. You'll get a better contraction.