My ULR checker is all over the map....I just ran a phosphate test and the first round said ".82".....I ran it again and it's now showing ".01". This has been happening consistently the last couple of weeks. I'll run 3 tests and 1 is always SKY HIGH....am I doing something wrong? The only thing I can think is that I'm rinsing with tap water (the vials) and letting them air dry. Would that cause a bad reading? What gives?