Acceptable ph range for cannabis to uptake nutrients in soil is between 6.3 and 6.8ish. If you wander out of that range, you'll lock-out nutrients and plants will suffer.

I start the grow on the high-end of the limits knowing the buffering capabilities in my potting mix will fade after 6-8 weeks. I somewhat time my transplanting to fit in this schedule. Especially the final transplant 2 weeks into flowering.