That's it. Your LFS
played you by saying there are not enough bacteria in your water.
As for the Alk
issue, are you planning on this being a reef tank? If not, Alk
is not near as important. That being said, you're still quite low. Unfortunately your pH is already high end and trying to raise Alk
alone you will be stuck with the buffer solutions you have (i think). If your pH drops tho, I would use baling soda instead. It will raise the bicarbonates better but will raise pH as well (which is why you shouldn't use it now).
I have always used baking soda for raising both pH (indirectly) and Alk
in my aquariums, pool and hottub. ITS CHEAPER too.