Agree with the above
Where I lived in the US, the KH (calcium hardness) of my tap water was very high, and Total hardness at about 250ppm, so in tandem, the alkalinity was also high, all together, resisted pH change.
Fot certain fish I added leaf littler and tannins from
soaked leaves, and it would barely drop pH by more that 0.20.
I used the leaf litter and tannins more for their anti-bacterial quality, rather than the mediocre drop in tap water pH.
When you snorkel in low pH leaf littered areas, you might find the litter is up to a foot thick, and cover an area of a city block from constantly dropping tropical vegetation.
This is the kind of accumulation that actually can influence the lowering of pH of the surrounding water.