I cannot explain the CYA test result change. Today I took it and read it by a window natural not bright light. I 'm not quite sure of the conditions last time. I will test FC and CC in the morning and add more bleach accordingly. Then I will test again at night and add to bring it to 15. It should of reached at least 14 after all the bleaching tonight!
Thank you for all your help Dave and have a wonderful vacation.