Closed Loop 4 Sensor Control System
There are many ways to attack this, and the best solution depends on details you haven't told us.

If these motors don't need to move smoothly, then it can be as simple as turning off or turning down the ones in front, and maybe boosting the ones in back.

Another approach is to control each motor independently such that each motor is always within 1 inch of its desired position.

Yet another approach is to pick one as the guiding motor, then have a control loop keep each of the remaining motors within 2 inches.

A lot depends on what kind of position and speed feedback you have, and what kind of position and/or speed control you have over the motors.