Hello! I'm new, but have lived with this pool for more than 40 years. For the first time ever, we cannot hold ANY chlorine. Our pool store sent us home with a quart of CYA and our level has hovered at 100 ever since. This weekend we drained a foot below the skimmer and refilled. Now our CYA is 80 to 85. Shocked this morning with 2 gallons 12.25% bleach and chlorine was gone within three hours. Any thoughts? So appreciate y'all's help!