Bart, remember how I was dosing magnesium when you came over? Well, the coralline burst out bright and happy on the back wall again of my tank. I would like to say I doubt it is possible to overdose the product, but obviously there are limits. If you can get your hands on the Dow Flake stuff I use, I'd use a pitcher filled 50% with magnesium chloride to bring it up way higher. Your goal is 1300 typically, although the true number is 3x the calcium level.
You could always dose 25% of the pitcher two days in a row to avoid adding too much too soon, and test the progress after the first 24 hours.