I concur with talldutchie, and will just expand a bit as to why your chemicals are not working to lower the pH.
The pH is only one part of two (or perhaps three if one separates GH and KH) issues, namely hardness (GH), carbonate hardness (KH or Alkalinity) and pH. These three are related, though high GH does not mean high pH and vice versa. The pH is "buffered" by the KH to prevent fluctuations. Depending upon the KH of the water, this buffering can be significant, and any attempts by adding "acids" in the form of these pH adjusting chemicals will fail because the KH is negating them, in a sense. But the fluctuations during this is far worse on fish. And, it is possible to keep dosing the chemicals up to the point where the pH buffering of the KH is exhausted, and then the pH can suddenly crash which usually is severe enough to kill the fish outright.
As talldutchie said, the only effective way to lower pH is to lower the GH and KH by dilution. Now, having said that, in water that is already low in GH and kH but high in pH, the pH will usually lower by itself as the organics build in the substrate. And using dry leaves, peat and such can lower it too by adding tannins.
I authored an article which may help to explain all this better, you can find it here:
Byron Hosking, BMus, MA
Vancouver, BC, Canada
Something we all need to remember: The fish you've acquired was quite happy not being owned by you, minding its own business. If you’re going to take it under your wing then you’re responsible for it. Every aspect of its life is under your control, from water quality and temperature to swimming space. [Nathan Hill in PFK]