In order to help you get answers, most people here will need more information.
you’ll need to provide more information on ammonia, nitrites, ph (tap and tank water), gh, kh, temperatures. What’s your tank size? What do you have stocked in it?
what do you use to de-chlorinate your water? Etc.
also, I’m rusty on the chemistry, but if your tank and tap water are varying that much in ph, is sounds like an imbalance. The rocks you have, are they store bought? Or did you find them outside? If the rocks aren’t chemically inert, they may alter your ph. Again, I’m not 100% sure on the chemistry of it, but these are some of the details you may need to give here so that others can help you solve the problem.
good luck, and I’ll keep an eye out for more replies...
Edit: typos