Rain water and Promix - No need to PH??

Im looking to collect rain water in my 2 (200L) rainbarrells and use ti to mwater my ourdoor girls this year. They will be in 100% promix HP

Ive never used promix nor rain water so any advice is appreciated.

I will be filling the barrells with rain water, then diverting the gutter water to the drain instead of overfilling to barrells. I will be adding GH 3 part flora series to the water to use as my nutes.

Do you think the promix has the natural ability to adjust the PH to a perfect range for cannabis?

I use a different peat mix but it basically the same as promix hp. I don't ph and haven't had problems, the lime helps keep it nice and buffered plus the nutes bring it down to 5.8-6.2 anyways once I start adding enough. The ph gets fucked if you have lots of bicarbonate in the water which shouldn't be an issue since you're using rain water. Always water with a decent amount of runoff don't let it dry out too much between waterings. I like to use a wetting agent a couple times to keep the peat nice and hydrated.

Good sound advice thank you.

Im doing one girl outside, in 20 gallons of promix.

Check your rain water ph, if you live by a coal plant you may need to adjust .