i just tested my soil's ph because i suspected it was off. the plants seem to be growing kind of slow and the leaves are starting to look unhealthy. I think it may have started when i started using advanced nutrients. I just tested my soil with a cheap ph soil tester and it showed green for high (ph > 7) and yellow for low (ph <7) and it was really dark green. i only have 2 plants currently but i plan on expanding to more. How expensive are legit ph testers? should i buy a digital one or something? my chemistry teacher said the ph of our tap water is around 6 - 6.5 and that i could borrow her ph meter if i wanted. i just dont what to tell her its for.

what ph do i want for my soil?
do advanced fertalizers for veg have high ph or low ph?