So I do my routine tests as a part of a SLAM but leave all the chemicals in the vial (lazy...and I was up at an ungodly hour to test). Anyway, overnight test has FC 15 and 0 cc but left it there and this morning (ok, was morning before too - but now everyone else awake) and the chemicals/water in the vial are now purple instead of clear. Explanation anyone? (evap of chlorine?)