I'll post the initial numbers before I go into the question:
Since I got the CYA down from 500 everything had been good with the water. I have kept FC between 6-8 (I know, maybe a little low but wanted to be able to test PH). I normally keep the PH between 7-7.2 due to metals in the water.
Last Sunday we had a lot of people in the pool, a large rainfall of 2" (don't roll your eyes Texas people), and I added some Metal Magic. Every day after that the water got slightly cloudier. I slowly raised the FC level until a high of 12. I performed an OCLT every night which passed each time and never had a CC of more that .5 over the time period. I read one thread in which Jason had commented that high PH+TA+CH can cause cloudy water. As you can see the PH wasn't really high, just higher than I normally have it. So I put the recommended amount of muriatic acid in to get down to 7.0 last night. I got up this morning and viola, water is clear again.
So what gives? Does lowering PH normally clear the water in and of itself? Could I have had an algae bloom trying to start even though there was no overnight chlorine usage? Does metal magic or other sequestrants cause cloudy water?
Thanks for any insight.