If you went from sundown one evening to 3:30 the next afternoon without losing any chlorine that is good. But, then it is odd that within the next 24 hour time period, you lost 7ppm. Personally, if it were my pool, I'd do the overnight test one more time.

Here is your choice. If you continue to use the trichlor tabs, your CYA will continue to climb. As a result, you'll have to run higher and higher chlorine levels to compensate for the higher CYA. Or, you can use the tabs for a little while to bring your CYA up some --- maybe try 60ppm or so --- and then switch to bleach and see if that allows you to go to adding bleach every other day instead of every day.