spa plaster looking dingy?

Our pool and spa is only 1 1/2 years old. The spa looks like it could use a cleaning. The owner came out and told us to use muratic acid to get rid of the light cream/yellow color. He did try some and wow...it was back to being white again. So we said OK we can do this ourselves and then realized that the small area he did became a little rough. Has anyone ever thought of using bleach in the spa, to bleach out the old color and bring out the white again? Maybe this is not a good idea? Any help appreciated!