Hey Honda,
IMO, don't solely trust ANY single source of info, especially a LFS. From the stores point of view, they sell more stuff when people's tanks go south. Either in medications, or more livestock because yours died.
Regular water changes are by far the best way to keep your tank in good health. I do weekly 15 gal changes on my tank, giving me 60+g a month on a 200+g system. With few exceptions, my tank is thriving, and has been for years.
I can't help but notice this thread is called" is my coral dead?". We all have issues occasionally with a certain coral or fish from time to time, i have one right now that I've had for 5+ years that I'm having a problem with, but regular water changes will definitely make this happen less often.
Please accept this as friendly advice, and not just bashing. Best of luck in the future!