Post a full set of test results including FC, TC, pH, ALKm CH, CYA, and Salt and also the finish of the spa and pool (plaster, fiberglass, vinyl) so the good folks on the forum can get an idea of what is going on in your pool. Also, what type of filter are you using and is the pool new construction or an established pool. It would also be helpful to note any other chemicals or additives you might be using (enzymes, clarifiers, metal treaments, algawcides, etc.) The airation from the spa jets sometimes can cause some products to create more of a scum line in the spa than in the pool.