Sounds to me like you've got an algae bloom trying to happen, and the amounts of chlorine that you've been adding is just enough to keep it from completely going green but not enough to actually kill it. With your CYA level at 50, your chlorine level is way too low....and it's that much worse if you actually had a CYA of 70 prior to the party. You need to add enough chlorine to get to approximately 20 ppm, which for your pool should be about 7.5 gallons of 6%. Add it at night after the sun is off the pool, and check again in the morning before the sun hits the pool. If the level is lower, then you just need to add chlorine to get back up to the 20 ppm, and continue to do this 2-3 times daily until you no longer lose chlorine at night.

Stop adding all that other stuff--you're adding to the problem and not doing yourself any good. Stick with just plain bleach. I would also increase your pump run time...you need to run it 24/7 while fighting an algae bloom, but even after it clears I would run it a minimum of 6-8 hours daily during the summer.

Janet