First let me state I have ZERO experience with promix. With that said I have grown in hydroton via power growers and DWC with 10-20 gallon tubs as well is traditional store bought soil grows and homemade compost and vermicompost grows all the while brewing my own teas and applying them accordingly. Never have I ever PH'd a Bennies concoction. The idea of ph'ing nutes is so that the plant can absorb nutrients faster at certain ranges depending on the medium. The reason for beneficial bacteria are to create a thriving root environment that allows the absorption of nutrients. Depending on what you decide to use to adjust your Ph you could kill some of the bacteria or Fungi, thus making your concoction useless. Some fertilizers tend to destroy the bacteria in soil so most people either use one method or the other, but like I said before I have ZERO experience with promix and you may in fact have great results combining methods.