Thanks for more details.
If you're swimming 2000m in roughly an hour, that puts you around 3min/100m. Hip drive focus won't help you much at this phase, only stability or stabilizing your vessel to swim in the smallest drag profile. You must be dragging hips through the water, drag profile is huge at 3 min 100m pace
At 18 SPL, what tempo range are you working in? Do you use a tempo trainer?