pH testing question

[jp80911]

Picked up a bag of pebbles gravel from Lowes two days ago to do some pH test see if it will change my water parameter, it's so darn hard with the test kit I bough from PetCo. (fresh lab, by red sea)
With the solution for 6.2-7.4 the color turns out to be very blue, same as 7.4
so I tested with a different solution for 7.4-8.6 but I couldn't fine any matching color, does that mean my pH is way over 8.6???
Could it be the lighting? maybe this should be done under sun light or real "white' light? anyone had this kind of issue before?

 

[jp80911]

is there anything that can put into the tank to keep pH level down? and I don't mean chemicals.
Will plants and drift wood help? do I have to replace with some fresh driftwood over time or it will always help to keep the pH level down?
I think my tap water pH level is around 7.4 if i use the gravel from Lowes it's probably close to 8 and I'd like to keep it around 6.5-7 if possible.

Thanks