What is in your tank. Wood(Bog) will drop Ph. Some gravels do as well.
Algae bloom can also drop Ph.
Short term you can use baking soda to raise the Ph. I think that is what 'Ph up' is anyway.
Do extra water changes, Hamilton Ph is around 7.4
Add shells or bird grit, these will help in the long termas a buffer. I think these will also change the water hardness.