3/4-gallon of 10% bleach in 15,000 gallons per day is 5 ppm FC per day which is definitely high. Something in your pool is consuming chlorine. You should do an overnight chlorine loss test to see if it's just related to intense sun (and perhaps the CYA reading is off) or if there is something in your pool water consuming chlorine such as algae growth or some chemicals. Your FC should be high enough to be staying ahead of algae, but perhaps there's some nascent growth that needs some shocking. The overnight test can help figure this out.
You might also double check your bleach concentration. 1/4 teaspoon of 10% bleach in 2 gallons should be 16 ppm FC (1/8th teaspoon should be 8 ppm FC). Maybe your bleach isn't as strong as you think.