I wouldn't worry too much about your pH. Unless you are breeding the fish or dealing with wild-caught fish, then you need not worry about the pH too much. I have tetras, rams, bettas, plecos, gouramis, etc. that appreciate soft and slightly acidic water. However, my water is moderately hard and is neutral/alkaline. I really think you should leave your tank as is. It is better to have a consistent pH than it is to have a fluctuating pH. If you really feel the need, you can use some black water extract or some peat moss in your filter. However, this will not cause a drastic change unless your water is very soft.
Just my 2 cents.