The problem you mention was not caused by concrete dropped into the pool, but by high pH levels combined with high temperatures (due to the cover and...

You could try 2-3 ounces/10,000 gallons/day as a starting point, and measure the free chlorine levels to fine tune it for your pool. No two pools are...

Makes logical sense to use unstabilized chlorine as your pool water has reached the upper limit for stabilizer.

LOOKS LIKE YOU ARE SITTING AROUND 100PPM WHEN IT SHOULD BE 10-30. YOU NEED TO DILUTE IT OR PUT SOME JACKS MAJIC AFTER SHOCK IN TO LOWER IT.

Are you changing your water very often? Cyanuric acid normally never goes away, unless you have a leak and are constantly refilling your pool.

Has it been really hot & sunny where your are?

Are you covering your pool at night?

These can lead to chlorine loss.

The stick chlorine you use probably has a pH of under 3, and may be lowering the pH of the pool water. Low pH or low total alkalinity can result in...