However many corals you fit in the tank depends on what kind of corals they are and what type of defensive mechanisms they have, and even when you introduce them into the tank. Corals are living, breathing, reproducing creatures that need tender loving care, they aren't just ornamental displays of color...
You must do research on each and every coral that you purchase, what water conditions they like, what they eat, what their lighting requirements are and what their defensive mechanisms are. You should also research fish first, because some fish eat corals!
The guy at the lfs made a pretty good profit with you buying all of those supplements, lol. Supplements aren't needed as long as you do water changes. Which, I'm sure you do at least once a month.
The only supplements I've used regularly is kalkwasser which is a calcium and alkalinity additive and phytoplankton, which is basically coral food, and it stimulates the growth of zooplankton.
If you aren't feeding your corals already, research the corals you have and then figure out how to feed them.