Average ppm loss on BBB?

[KurtV]

My CYA level is at 70. I don't think that is the issue.
My guess then is that your chlorine is fighting something.

It was in the mid 80s and sunny all day yesterday, but there were only 2 of us in the pool.
That probably accounts for at least 2 ppm of loss.

However, we have had a lot of thistle seed tufts that are blowing into the pool from the lot next to ours...
That may account for a bit more loss.

I'm guessing here, but I think you have some additional chlorine loss that's not accounted for by the known consumers. I recommend you bring your chlorine to shock level (per Ben's "Best Guess" table) and keep it there until the level holds overnight.

A full set of numbers would still be helpful.