Go to any store with a garden department and buy one of those green pH+moisture+light meters, they're easy to find, they have 2 rods, one copper, one zinc, that you stick into the soil.
This way you'll know at least if you're in the proper range.
Do you actually believe that these guys test their soil's pH before selling it?! That would mean that there would be no more threads or posts regarding pH problems, and at least a half of those growers have miracle grow or fox farm soil.
Before they sell soil, they check the pH once, then load up hundreds of bags before checking it again, you may just have had a bit of bad luck, happens soooo many times.