I think I figured out your problem. I just ran some numbers and I don't think you are adding enough bleach. I'm estimating your volume to be around 11,400 gallons. In that sized pool, each cup of bleach would only add about 0.5ppm of chlorine so that means that when you add 1-3/4 cup, you are adding less than 1ppm of chlorine.

A quart of 8.25% bleach will add about 1.8ppm of chlorine and one of the 121-oz jugs will add about 7ppm. Use those as references to help you figure out doses. If you really do have a CYA of 50-55, each evening when you test your water, add enough bleach to take your chlorine level back up to 6ppm.