Hi Jazser,
One recommendation i have is try to add more spa down to the spa, dissolve first, but do NOT circulate. By doing so, the chemical creates an acid pocket within the spa and it seems to lower the TA faster than when it is circulating. I would only let it not circulate for about an hour or so. Im not sure how many gallons your working with but for a 350 gallon tub i would use around 3 oz. of a PH Decreasing chemical each dose. Try it out and see what you think. Good Luck!