An electric current is most likely to affect the fish first, invertibrates last. The more advanced animals with a central nervous system that are closest to the source are the most affected normally. Corals can close up for protection when things aren't going their way. If the fish are fine, the corals should be fine when you have everything corrected. The recommendation for carbon is always a good idea in such cases as stress can cause a release of toxins from some animals. I would look for more documentation on the chlorine removal idea. Cl- must be present to balance other major ions in solution in sea water and turning it into a powerful oxidizer with a little stray voltage in a tank seems to me to be unlikely.