If you miss your deadlift at your knees or around mid-shin height, it's common to hammer away at RDL's, good mornings, and other variations to train your posterior chain. This can be beneficial, but without a strong upper back those supplemental lifts won't do a thing.
That's why chest-supported rows should be a staple in your program when training for a deadlift PR:
Chest-Supported Row
Likewise, strong lats, traps, and rhomboids are undervalued when training your deadlift. Increasing their strength will ensure that you can keep better mid and upper back position during your pull, especially when the bar hits mid-shin height.
Chances are if you're over 30 that backside of yours is starting to look like two gluten-free pancakes, even if you train. Here's why and how to fix it.
The Shotgun Method allows you to train for both size and symmetry without having to skimp on either. It actually allows you to concentrate on the big lifts without neglecting isolation exercises that address lagging body parts.