Total alkalinity in my spa was quite low, so I added Alkalinity Up. Now when I test for alkalinity (using brand-new test solutions), the water in the tube turns light blue rather than green when I add the second solution. When I add the third solution drop by drop, eventually the water turns yellow rather than red.
Using the same new test kit on my pool, I get normal results, so I don't think it's a problem with the test solutions.
Any ideas what this means?