It takes time for things to change in a reef tank, are they doing any better? At night do you see anything on the polyps eating them? Do you have other corals in your tank and are they doing good? Do you add supplements to your tank and not measure to see what their levels are?
I wouldn't trust your local fish store, you should try and find another one around your area. They have given you a lot of incorrect information. When I am looking at a new fish store I look to see if they have a display tank that looks good with nice big colonies of corals. If they do that shows that someone in the store knows what they are doing. I also look to see if they have many dead fish in the tanks. I know that sometimes things happen and a fish will die but it is good to see that the employees will take the dead fish out of the tanks.