Hi, Bass,

The only answer that makes sense to me is dusty guests!!

Your numbers give no clue to the problem and that it clears up overnight is good news but puzzling as well.

I would also advise you to raise your CYA into the 30-50 range but lower CYA would not seem to me the cause of your issue.

Is it possible you have some type of sediment on the bottom that is not getting vacuumed? That's my only logical thought.