It turns out that maybe the new test is right. I took a water sample to a LFS and they measured 600. I bought a Nutrafin kit and it measures over 600. I guess the Seachem kit that always agreed with my old Salifert kit was wrong. That's five different tests, three say over 600 and two say 380. I wish I could have more confidence in this stuff. I have some old reference solution I can try. Does stuff like that go bad?