Most buffers are chemically targeted to acheive a pH of 8.3 and stop. There is absolutely no reason to go beyond that. If your daytime pH is reading 8.1-8.3, you looking good. It is also not uncommon for the pH to drop fairly low at night eventually reading as low as 7.8 just before lights on in the AM.
Be very wary of making chemical additions. Buffers will also increase alkalinity in the process and can easily upset the balance between alk
causing you even nore issues. Before you dose anything in the tank, always test first to see what is needed and again afterwards to see what the change was if any.
Do you have an alk
test kit? If so, what are your readings?