I have a 12,000 gallon fiberglass pool that had light blue finish when new. Now the pool is about 6 years old and the finish at waterline and below is whitish. In the past I had used metal off and even bought tester to check for iron and copper. The pool has been opened for about 2 months and initially I completed the slam process and now only use liquid bleach. Initially when I did the slam my cya was 0 so I raised to 30 but now is 0 again. Currently my free chlorine this am was 0.5, combined chlorine 0.5, alkalinity 80, calcium 160 and ph was between 7.8-8. Currently I know I need to raise the free chlorine but also need raise the cya. My question is about what to do to try and improve the staining.