Hello CC~ This is not gonna be a big help but I just want you to know what you might already know.
I'm in US and I use supersoil.. This supersoil company claims that their soil is PH balanced (5.5 ~ 6.5). I've used 7.0 ph'ed water from the beginning and I never had any problem so far. My TAP water's ph reading is 9+ as I said..
I used 6.5 ph'ed/filtered water last week and some of my plant showed a sign of nutrient deficiency(and possible nute burn, not sure). One of my plant was 6 weeks into flowering so I had to flush anyway. I flushed it today.
I don't trust my PH meter 100% so I have a pool PH liquid test kit as backup. I use PH liquid test kit to make sure that my PH meter reading is correct. I'm gonna buy PH solution to calibrate my PH meter next time. I guess I am just lucky with this soil.. I never ph'ed water that have drained from a pot.
That's all I can say. :thumbsup: