testing the runoff will show the pH of the soil decently.

But, I personally am one to not worry about it unless it looks like there may be a problem - it you watch carefully every day to see how they are reacting, you should be able to catch things quickly. i.g, I just found a white tip on ONE leaf on ONE plant out of 10. It may mean nothing, but it MAY mean that we have nitrogen deficiency - likely from high pH. Because my water is 7.2 normally, I have to make sure I watch carefully for these things. Tight money this time keeps me from having the correcter additives and testing kit, but I'll likely be doing so myself next time. I watch the plants closely instead.

Again, I'm totally new on cannabis, although I've gardened for awhile outside.

Oh, and plants ALWAYS can become root bound, but if you are doing a rather quick grow it shouldnt be too bad normally I THINK!