Not sure what's hurting my plant

[kabongster]

Lowering the pH of my water

Is it true that white vinegar added to water lowers the water’s pH? I know the water I will be using will have a pH of 9.2 after filtering. I know I want to lower that to 6.0-6.5 in the safest way possible for my plant. How do I do that, without spending a lot of money? If white vinegar works and is the best/cheapest way, then how many ml’s of white vinegar per Liter of water would lower my water pH to an ideal range? Thank you. Good luck growers. If it’s of any difference plant to plant, I’…