Any risk of not reducing demoted worker’s pay?

Q. We moved a salaried supervisor to a rank-and-file hourly position, but we left him at the higher salary. Now, several co-workers are complaining that they’re being paid less for the same job and grumbling about discrimination. The co-workers are of different nationalities than the former supervisor. Should we raise the co-workers’ salaries if we want to be as cautious as possible to avoid a lawsuit?