quality potting soil i have tested has always been 6.5-7 and some have it listed near the 'ingrediants' section on the bag. humus is just rotted forest products and too much is not good. cannabis likes a sandy-loamy soil with good drainage...iow, it hates sitting in wet ground constantly and must have good drainage to thrive. i use the best potting soil available and blend with cactus potting soil plus a little perlite...

it's just as important to check your water ph too...if not moreso.