What I do is put some cc in a bag and float it in the tank, it helps buffer it. Don't add chemicals, they only cause huge ph and alkalinity swings. Good luck.
i don't have an alk and calcium test... but everything else is 0 amm trates and trites i just noticed my rock was changing a funny color, did a test and low pH
Check Calc, Carbonate/Alk, and Magnesium. It's probably one of those are low causing the low pH. Get it tested at an LFS if you don't have your own kits, but I think its worthing getting the kits for your own uses.
My 2 cents...
Of all the questions your being asked and of all the recommendations your being given. Start with the basics.
Answer Sep's question first.