I'm guessing that your calcium levels were low enough that coralline algae was having a hard time establishing itself in your tank. With the addition of the Ca
, you now have enough of those elements for coralline algae to thrive... which is what you're seeing with the green/purple/red spots.
What kind of salt are you using? Depending on the salt, and your water change schedule, you may or may not need to use those supplements - or at least not all of them. Some salts do require a little boost in calcium to really get the coralline algae going over the long run.
As melosu mentioned, in order to make sure you don't push your water parameters way out of whack, you should really test for anything you put into a tank.