I bought a Hanna Alk checker from a lfs and been using it for about a month and was getting readings of 9.0 9.2. I was thinking thats great, I decided to get my water tested at a lfs and they said my alk was 7.2 I didn't think that could be right so when I got home I rechecked my alk and it was 9.1. So I went to a different lfs to compare the test and they also said my alk was 7. So now Im thinking its my checker. Has anyone else had an issue with theirs. Also I only use RODI water to clean the vials, and make sure there clean and clear before putting them in the checker