PH Levels are still low

Hi All

I have recently set up my first Marine Fish only tank (30th April). I have just tested the water, and here are the results. PH = 7.6. Nitrate = 10, Nitrite = 0.2, Ammonia = 0.2.

I know that the Ammonia and Nitrite should continue to reduce, but my question is do I need to do anything to increase the Ph levels? If so, what?

When should I do my first water change?

Thanks