From what I've heard the soil testers are mostly crap, especially at Home Depot. You need a PH tester for the liquid you are pouring in. The idea being you put your water in the pitcher, add in your nutes, then check the PH. Then I usually adjust with a little PH Up solution and test the solution again. When it is right, I pour the pitcher or mix into the pot. I like the strips because it helps with a baseline distilled water read until I dose it. For whatever reason, the PH meters have hard time measuring distilled water because it is not buffered with anything. I also keep the strips handy to keep the meter honest. Those things need to be recalibrated every now and then and you want to make sure you are getting an accurate read. If you buy a PH meter, you will most likely need to get some 7.0 PH solution to continuely callibrate it.
If all this sounds expensive or like it's too much work...it is one of the more important parts of growing. If that still doesn't motivate you, just get the strips they are like $5. But make sure you get them at the hydro store...I have gotten some shitty ones at drug stores that don't work.
At this point, you can improve your situation in the grow, but you really need to take this to heart and iron out the wrinkles for the next one as I am sure you do not want to make this mistake again. The bottom line is that the more leaves and the healthier the plant, the more bud you will yield.
You can look around here for recs on specific brands. I use a Hanna meter and the strips are called pHydrion.