Extremely low dKH

I just set up a 36 Gallon tank a few weeks back and put some live rock in there and let it cycle for a while and used RO water. I now have two tomato clowns and some snails aswell as one shrimp. the dKH in my water is very low and I am trying to get the tank ready for corals. I use a few chemicals (Purple Up, Liquid Calcium and a few others I bought from Kent Marine. I have only used the Calcium once and the Purple Up once a night (only about 3 ml a night). Is their something I can do to raise my dKH? I am new to this and need a little guidance.

Thanks:help: