gel coat stains after soda blasting

[sbjr]

We had our hull soda blasted in the fall of 2012. During the proceedure, the soda residue got all over the boat, including the top deck. When we rinsed the soda off the boat, the gelcoat was stained blue, green and yellow. (Basically, it looks like 1980's cultured marble). While we are on the hard, we have tried many marine cleaners RV cleaners, and vinegar. Nothing seems to help. The side of the boat with the most sun exposure is fading, but the other side is still very dark, and we will be on the hard for a good while longer. Are there any chemists out there with the knowledge of how to remove these colors from gelcoat?[/size][/font]