lol you know if i haven't tried comparing the results with drop test so many times i'd go buy a new probe for my tester after that post of yours. i cant believe that you've been off by 0.4 no way except if you managed to find some really bad brand i tried them countless times with drinking water from closed bottles they give me the same ph as written on bottle, i've tried them when they're old and they still worked and all i had to pay was like 10$ every 400tests. and if you say that 5.8 on meter was 6.2 in drops so you're suggesting a + or - 0.4 that is 0.8! why do they even sell this stuff? maybe your metr was off
i'll show you some pics of the experiment on ph drop test with bottled water and you'll judge for yourself i'll take the pics next time i visit my growroom will be posting them by tomorrow