you should get just a 14 dollar ph test kit, with up and down, i use general hydro, and I would also suggest using just a little mychorizae/benefical bacteria, i use great white, and something like fox farms, 3 part nutrient, a part is grow, one is guano etc, the other is bloom. your plants look pretty good for potted without any nutes yet. Also i got a cheapo soil ph/light/moisture reader for about ten bucks, the one i bought doesnt even take batteries, not accurate of course