[Myka]

You need to use an ammonia binder to get ammonia back to zero. Prime or AmQuel do this by converting toxic ammonia to non-toxic ammonia. When you use these products many ammonia test kits will give you false readings. The API ammonia test kits are cheap, reliable, and are compatible with ammonia detoxifiers. SeaChem offers an "Ammonia Alert" tag that sticks to the inside of the tank. Although I find these badges to be terribly inaccurate as far as the readings go, I do find they will accurately let you know there is ammonia present by changing color. Dose as much AmQuel or Prime as you need to in order to get ammonia to zero. Follow the directions on the bottle for a good dose size, and re-dose as many times as you need to.

I am also skeptical about your use of tap water. You never know what is going into your tank. What is ok for drinking water definitely isn't always ok for a reef tank. Since waterchanges aren't helping, and almost seem to be making things worse it makes me wonder if the water isn't the culprit. It's an unknown for sure.

Another thought is the kalk treatment for the Aiptasia. How much kalk paste would you add to the tank each time you treated? How often would you treat? I'm wondering if you caused a pH spike which led to a "rock slide".

If you're testing pH with a drop test kit, then the reading is almost as good as useless since these test kits are not very accurate, or at least not very reliably accurate. Imo, the best thing to do with pH is to either a) don't test it at all, or b) test it with a calibrated digital pH meter. Did you double check specific gravity as Steve suggested? Just take a sample of your water into your LFS and get them to check it with a refractometer, not a hydrometer. Which refractometer do you have? What do you use to calibrate it?

Did you say that you turned off the powerheads because they could be a source (of something?)? Don't turn the powerheads off! The corals need water flow.

Also, as a side note...live rock doesn't "wear out". There are many, many tanks out there with 10 or 20 year old live rock that are still going strong.