A question for the collective hive...

I made a citrus mead (my second) this weekend using fresh squeezed key lime juice, kaffir lime leaves, OB honey and 71B yeast. I decided to go ahead and add the juice to the primary vs. the secondary (which went against my normal judgement anyway). The initial pH was terribly low at 2.6! I was concerned about the pH being way to low for healthy fermentation, so I buffered it using calcium carbonate (CaCO3) for a pH of 3.2. The fermentation started slow (20-24hrs.) and seems a bit sluggish for my sensibilities. The question is... should I add more CaCO3 (or something else alkaline) to raise the pH even further or leave it well enough alone and just keep monitoring it? In addition, can I expect the pH to drasticly drop as the fermentation nears completion? I had some similar pH problems with my last citrus (orange) mead and simply gave up. I've got way too much time invested squeezing all those little limes to give up on this one! TIA