Hi Got your pm..
first off take a step back. The ph swing is not a big deal ..its not going to make your fish act as they are.Something else mist be going ...pH 6.6 to 7.2 may stress outbyour fish a bit but will not do what you are seeing. Even the ammonia readings you are seeing wont cause what you are seeing .Is there anything else that you can think of thats changed since their behavior has. Are you sure your tests are accurate as far as water parameters?
al