First off, have you verified that your PH kit is good? If not take a sample to the LFS and ask them to test it, preferably with a different brand than you are using.
Second, why are you trying to change you PH? That's a really good PH and stability is much more important than achieving a specific PH. Unless you are trying to breed fish or want to keep fish that have to be kept in a high PH (cichlids fall into this category, I think) there's little reason to mess with your PH.
If you actually do need to adjust your PH, crushed coral or baking soda are your best options.