What is the pH of your tap water?
If tap is 7.4 then tank pH won't lower with a water change.
It is better to have a constant pH then fluctuating. Driftwood and Indian almond leaves can lower pH.
Why do you want to lower it?
Most fish adapt just fine to that ph, several of my fish are wild caughts and are doing just fine is 7.6ph.
If a pet store has advised a ph of 7.0 that is just them trying to get you to buy more stuff that will be harmful in the long run, stable ph (same as you can get it from tap to tank) is better for fish in the long run, most domesticated varieties of fish now are able to adjust to ph and tank parameters just fine.
Well it's just that I read that a lot of the freshwater fish like a pH around 6.8. But having learned from previous lessons I don't want to tinker with the tank just to tinker with it. I'll take everyone's advice and leave as is. I just want to have a vibrant tank of fish and after I got bad advice at the fish store about aquarium salt...I come to the "pro's" on here for guidance now. Thank you all!