Ive got a meter from 2011... You think the probe is still good? Cause I'm starting to question my TDS meter. Dutchmaster says something like 13ml PER GALLON. So I question that... and I question my meter. Either I'm under feeding because I only paid $15 per bottle of dutchmaster (aka DILUTED) or my meter is wrong and they've got salt build ups. I bought a new PH meter like 2 months ago and calibrated it twice... so I know the PH is right on. I want beautiful green leaves, universal growth (no awkward leaf shit), and the "praying" stance. Grrrrr.