m0useanswered grow question 2 years ago Your mix sulphur into the topsoil and water it in, its that easy. a little goes a long way don't want to over do it. Can be found at most garden supply stores.
if you have 4 meters all saying the same thing, then they are prob right, I don't know the models you use or brands so can't comment further on it.
The one I use does require calibration quite a bit and I have solutions that help me get it back into range. a 4.01 a 7.01 and a storage solution.
I think the advice of not worrying to much on PH is good. my first couple of grows I did not use a PH pen at all. Next grow can focus on the composure of your medium for what works best for you.
Like grannie said, anytime you tag someone in the questions part of the website it does not notify the user. there is an inbox function on the site, its in the lower right hand corner, green/white paper airplane button, you can reach out there to other users.
Good Luck!