Wow, someone did a quality job for your home: 2700 square feet with 18 zones. My 9,500 square feet has 6 zones. Should be a lot more, but it is what it is.
You’ve done well measuring your water usage and square feet. If I were you, I’d measure the water usage for each zone, and calculate as best you can the square feet for each zone. That should hopefully give you an idea where your high use areas are.