That plan SUCKS!!!! lol I'm messin with ya.... foxfarms soil is good stuff.

Seriously though there's some major problems with the plan:

-the guano will burn seedlings
-you HAVE to feed your plants; cannabis is a pretty heavy feeder and just the soil nutes won't come CLOSE to sufficing... like, where is your nitrogen going to come from? If you said you were mixing in blood meal for your N source you would be getting closer... then you still need Potassium and micronutes. Liquid ferts are a growers friend... get familiar with them.

As for soil pH, get yourself some liquid pH indicator.
Measure the pH of your tap water.
Flush your soil.
Measure the pH of the water that comes out.
For example, if your tap water is 7 and your runoff is 6.5, your soil pH is less than 6.5... get it? There's a sticky about how to do this I think.