I have horticultural pH drops and some capsules for soil testing, which I only really use out of curiosity or if I am having any problem. Soil organics growers, in my opinion, do not need to be constantly fussing over their pH and checking it frequently; I don't anyways. Good organic soil is rich in humus (thoroughly decayed organic matter) which has a high cation exchange capacity. In short this means that your soil should both retain nutrients and resist rapid fluctuations in pH.
The next step to ensuring this is to have a sufficient amount of dolomite limestone in the soil. Dolomite has calcium and magnesium, and it counters the acidity of fertigation solutions; it raises pH. Soil flora (micro-organisms) and the plant roots themselves will also influence soil pH (e.g. by exchanging H+/OH- ions for others). Soil microbes like bacteria influence soil pH by utilizing H+ ions, thus reducing soil acidity (increasing pH). Most bacteria like alkaline conditions and actually produce an alkaline film/slime in order to help them survive. Fungi on the other hand tend to prefer moderately acidic conditions. All of the interactions between the roots and bacteria, fungi and other organisms in the soil tend to help balance the pH out.
Short answer: never hurts to add a little extra dolomite limestone. Be sure to water more dolomite into the soil every few weeks. You can collect and check the pH of the run-off (preferably the latter drops of it), but it may not be exactly what the actual "soil water" pH is. I tend to think it might be a bit higher, or perhaps a bit lower... but with the required additions of dolomite I don't seem to have any problems with my run-off coming out between 6 (yellow) and 7 (green).
Also aerating your nutrients/tea brewing will help reduce acidity.