Good morning. My pool is now open for the season 10 days. The water looks perfectly clear (but is still 65 degrees). Free chlorine test yielded 6 ppm with 0 cc's, but when I use the OTO test it registers no chlorine level. The ph is 7.6 , cya level mid thirties. Pool is 18,000gallon plaster. I'm using combination TCA and bleach for chlorination. Any ideas ?