You might have very soft water. I'd suggest your next step would be to find out your KH and GH. KH is most important. The five pack of five in one test strips often checks this if you don't want to spend a lot.
It would be much better to improve pH with more large water changes. Imagine if you have a bad smell in your kitchen and someone keeps spraying air freshener ... The air will be really full of gunk, and what would be healthiest is opening the window for fresh air.
If your KH is below 3 degrees, it'd be better for your fish to use small doses of api's cichlid buffer and cichlid salts (or seachem equilibrium) to keep pH stable. KH is critical to stable pH without adding so much to the water you induce osmotic stress.
My tap water is extremely soft ... Less than 1 degree KH and GH. In each not quite full 5 gallon bucket of fresh water, I use a quarter teaspoon each API cichlid buffer (for KH) and seachem Equlibrium (for GH) and I never have pH problems anymore. It sets both to about 3 degrees.
If your KH is above 3 degrees and your tap water is of a normal pH, you just need to do more water changes.
I used proper pH 7.0 for 6 months before someone taught me more. I lost a lot of fish that way.
People also recommend crushed coral but I found it to be messy and unpredictable.
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