Assuming you don't have a serious nitrogen issue, or a major heavy metals issue, I wouldn't worry about it. This usually happens with new rock. If your rock is covered with corraline when you get it, it is usually used to very different lighting than what you have in your tank. sometimes when I rearrange rockwork I will get some bleaching from stuff that was sheltered and now is exposed to brighter light. This is a very common occurance. I usually have at least one pincushion urchin in a tank as they like to eat corraline and will strip some of the dead stuff away, allowing new stuff to grow better.
The kinds of corraline that can live in your tank environment will regen in time. It takes a while sometimes though.
Keep up water changes, and put your lights on a timer. If you are going to dose anything, always test your water consistently. If your tank is that new, and you are doing good water changes (using quality salt re: instant ocean, seachem, tropic marin etc), you probably don't need to supplement anything.