A few questions here, then some answers.
How accurate are your current measurements? Were they done with recently calibrated equipment, or a clampmeter that's been kicking around the toolbox for 10 years?
What is the service factor of the motor? Also, does the nameplate list S.F. amps.
The current balance doesn't concern me in the slightest. In my experience, it seems very reasonable.
If the service factor is higher than 1.0, I wouldn't be concerned about the slight overcurrent. Lets say it's 1.15, (very common). You actually have an 86.25 HP motor which has been de-rated to 75 HP to account for overloads, voltage imbalance, high ambient, etc. If the S.F. amps are listed, that is the theoretical maximum current the motor can handle continuously in its maximum ambient temperature (usually 40C or 104F). If S.F. amps are not listed, it's not full load amps X 1.15, you'll have to guess. 93 amps on an 86 amp motor is not very far into the service factor. I normally don't advocate operating motors in their service factors, mainly because you're now what we would call an 'non-compensated test engineer', but you might not be overloading it at all.
Alot of centrifugal pumps will load the motor into the service factor when operated a low pressure. Some, particularly high pressure designs will grossly overload. The HP required by a centrifugal pump is related to the flow through it, not the pressure difference across it.
If it were me, I'd basically leave it alone. Make sure the overloads are properly sized, and it's not operated in too high of ambient temp., and you'll be fine. If you want to see lower current, throttle the discharge a bit (partially close a valve). This will reduce flow, and thus reduce HP.
