Lot# for K1000 0014 is 2123C; Lot# for K2006 0004 is 3024B. I always rinse the tubes before filling with sample water or going to a different test, but maybe I need to do a better job....will try that. Both kits are less than a year old, but will be a year in Nov/Dec this year. Will order more of both. Thanks for the help.