OK, some questions:
Are you saying you lose 4 ppm of FC between 8am and noon, with no one in the pool?
If there are people in the pool, who, and how many?
Do they use lotion heavily? Do they have leaky bladders? (Sorry, but it does matter!)

Changing direction:
Have you EVER used anything made by United Chemical: No Mor Problems, Yellow Treat, etc.?
Have you EVER used any other product sold in a 10" - 16" tall plastic jar, containing 1 - 2 pounds of white fine granular material that was supposed to help with algae, or in some other non-specific way, help your pool?

Ben