1.0 to 1.4 pH drops for the last 15 years.
Oddly, I've bred about 30 fish species somehow, grown more plants than I can recall, and never have had any pH related issue. Must be dumb luck eh?
CO2 is NOT a salt, so there's a HUGE difference between pH change due to salts, like say baking soda, vs say CO2.
Old advice specific to those NOT using CO2 gas for plants.
Once you add CO2, the pH thing goes out the window. Hopefully in the trash with the other myths.