RO water is the best thing you can do for your plants. PH of truly clean water means nothing, most high quality nutrients will remain very stable. Carbon filters are crap if you have a high tds in your starting water.
One of my grows the tds is 50 (ec X 500), another one of my grows the water is 500ppm. I am ordering a RO unit tonight. No mater what I do to the dirty water the plants show lockout of cal and K from all the sodiom in it. 95ppm of it. The reading obtained from the water company. Take the money you are spending on "magical bloom booster nutrients" and get an ro system, from experience I can say it is the best thing for your plants.