I dumped borates in my brand new pool this winter and continued to have high acid demand until 6 months or so had passed.
I went from 4 cups every 2 days to about 2 cups per week.
Sometimes there’s a drought, and sometimes you might be out of town for several days. An auto fill can help in that situation.
You can always shut it off.
I have a brand new jandy epump. When I run at 1600 rpm, it won’t fill. If I run at 2500, it will fill right up. If I go back to 1600 from 2500, it will lose a little water, but not much. It will usually hold that way for a while.
Is your air conditioning coil up in your attic? One idea is that you’re getting some condensation that’s getting drained from the drip tray under the coil and then out of a soffit and splashing down on your decking.
The drip trays are galvanized but they get rusty easily in a humid attic.