Agreed that you are going too quickly, only bad things happen quickly in this hobby.
I would also like to add that LFS's are notorious for bending the "params look fine" rule and giving bad advice. If you think about it, most every time someone looses something they go right out and buy another to replace it. Every fish you loose is another dollar in the LFS's pocket.... Sad but true.
I'm also wondering about the supplier of fish to the LFS, have you tried fish from only one source? Some fish collectors still do use cyanide to collect fish. It stuns them long enough to be collected and then in most cases the fish dies weeks later on.
What I would suggest you do is instead of spending more money on fish, spend the money on some good test kits. Go home test your water, and sit back and relax for at least a month before even thinking of adding another fish or coral.