Are you using a bottled water? Or is there some kind of filter on your tap?
Please post all the numbers, correctly identified.
GH in German degrees of hardness or parts per million
KH in German degrees of hardness or parts per million
It might. The bag says it contains Mg and Ca, which will raise the GH.
What else is in the tank? Any sort of limestone, shells or similar?
Have you been dosing any fertilizer? Either under-substrate tablets or water column dosing? GH booster? pH controlling materials?
Can you set up a couple of tests in jars?
1) Tap water, test GH, KH, pH out of the tap, after it has sat out for 24, then 48 hours.
2) Jar with a handful of Floramax, test GH, KH pH when you first set it up, then 24 and 48 hours.
3) If you have any stone, shells, coral or other material in the tank, test these, too.
GH is not really linked to pH, but KH is.