Seriously, pH is not a critical parameter in a planted tank. The reagent in pH test kits is good for use in a drop checker, but otherwise it is best left in the box. If you enjoy testing your water, just test with all of your kits and chart the numbers you get. This may be something interesting to look at from time to time. But, don't do anything to the aquarium as a result of those numbers.
Before someone jumps down my throat
let me explain more. Test kits, when calibrated carefully, can give you useful information, but you need to know what the information means and how important it is. I'm willing to bet that few of us fit that description. For most of us testing leads us to do things, or add things to the water that do more harm than if we had done no testing at all.
You can do fertilizing by monitoring the water with test kits, again only if you calibrate them carefully and often, but that is a lot of unnecessary work. If you enjoy doing it, then that type of fertilizing - trying to hit target amounts of each nutrient - works fine. But, for most of us, using a system like the estimative index system is a far superior way to fertilize, leaving us the time not wasted on testing for more routine tank maintenance, which will do far more good per hour.