pH of RO/DI water is essentially meaningless. pH is ratio of H+ and OH- ions, but your DI has removed virtually every ion in the water. While the pH isn't a perfect match, it's a very weak pH, with almost no resistance to change when any ions are added. Really nothing to worry about, IMHO.
Still, if you want to manipulate the dip pH for peace of mind, first step is to have a pH meter. For short-term change in RO/DI water, a tiny pinch of baking soda will actually LOWER pH. Baked baking soda, on the other hand, will raise pH in the short term. Both have the long term effect of raising alkalinity, which leads to higher long term pH, but that doesn't matter for the purpose of a dip.
If you overshoot pH, you can add a little of the other to offset. Be warned, it takes very little to effect a change, since the ion concentrations are so low. And once you overshoot, it takes more of the other to compensate, since you've significantly added the ion content of the water.
