Calcium at 340-360 is not that bad. Would you believe the big coral and fish corporation, ORA Inc., keeps their cal at sub-optimal levels and their corals grow just fine? Seriously. But I would up your cal and alk by doing a water change. Lots of corals and coralline will suck cal and alk out of the water. Alk can be easily up'ed by adding small amounts of baking soda, test then add more.
I like to spike my change out water with cal till it just starts to precipitate and then do a 50% water change. I admit this goes against the conventional way of doing a water change but it has always worked just fine for my tank.