I periodically test Alk and found it was about 12. Let it drop to about 10. In the meantime I bought a new kit(salifert). The new kit shows it at 13. Tested at the same time. Both kits recently calibrated with the included fluid. Obviously one or both kits are off. Just not sure how to proceed. I could buy another kit but that could be different from both. Then which one to trust? Neither kits are near expiration (2019 for both). Other than not dosing Alk for a while (assume it is on the high side), I don't have a plan. Suggestions?