First proper grow attempt (outdoor)

@TC_Connoisseur, Thanks again for an extensive reply. It's a lot of information to take in as I am completely new to nutrients, pH and all that, but the main reason I enjoy growing is because there is so much to read up on and learn about so I will definitely check out your suggested bonus reading. I am also positive that my tap water does not contain any Chlorine. The Netherlands has very strict rules on the quality of our tap water.

@Sauswaus, 8.2pH is pretty high for tap water, but I have no idea what your source is as we are definitely on different continents. Also a sticking point here if you are planning to use tap water and a soil with microbes to balance pH you will need to be very sure there is no Chlorine or Chloramine in your water, they will destroy your microbes that you believe are balancing your pH. Chlorine is easy to use a cheap aquarium air pump and stone for 24 hours and volatilize off, Chloramine requires a carbon filter to remove. The USA has mostly moved to chloramine so we have to carbon filter here. Now to address your questions, here is what I see. - Incoming water 8.2, outgoing water 6.0-6.7. Your water seems to not be heavily buffered (Low Total Alkalinity) or your soil is well buffered, either way your soil is doing most of the work for you and you should continue to adjust each time as you are, this will help but take a few waterings to build a buffer in the soil. I (almost) always pre-flush/buffer my soil a week before planting/transplanting and regardless of how much I trust the soil manufacture to do their jobs right. - Soil 6.2-6.9, adjusted water input 6.0, water out 5.9-6.1 I would suspect the reason for the pH drop in the run-off is due to water soluble nitrogen running off, nitrogen is potentially acidic and could account for that minor drop especially if your water lacks significant buffer, it could also be calcium(buffer) in your water getting bound into the soil. If you are measuring your soil pH by from the top half only you may be getting a higher portion of that calcium or other buffer from the water that is binding to the top layers as it runs through and the more water soluble nitrogen is hanging out lower in the soil. Now all of that said, I believe now that you have a meter and are on the right track with adjusting your pH you should be fine so keep doing what your are now doing. I also always suggest some Kelp/Seaweed extract in a Foliar Spray or even root drench also to give a quick shot of micro nutrients whenever a plant shows any stress. Also find out if you have Chlorine/Chloramine in you water, if you do you need to eliminate this before getting good organic buffering results, otherwise sticking to bottled liquid nutrients with pH up and down is the better route. Some Bonus Reading, If you have time and really love complex systems google both "soil ph and nutrient availability" to see what nutrients are most available, and also "Mulder's Chart" which gives each nutrients antagonistic and synergistic effects on each other...you'll probably hate trying to make sense of this but its good to reference as I never assume one issue is the cause of everything, in your case your pH is the big problem I saw but as you find out more it may end up being a nutrient that the soil is lacking or even one that is too high leading to a lock out situation at your particular pH. Everything is connected and the more data points you have the better your assumptions and corrections will be.

@TC_Connoisseur, Here is a short version of my latest update: pH meter just came in with the mail. Calibrated and took measurements right away. My tapwater measures at a 8.2 pH, which is even higher than I expected. What's confusing me is that the soil measures at 6.2-6.9. Flushed the pots for more measurements. - Runoff water flushed with the 8.2 pH tap water I've been giving them from the start: pH 6 - 6.7 differing between pots. - Runoff water flushed with tap water corrected to pH 6.0: pH 5.9 - 6.1 Now I'm wondering if - just like the Royal Mix I'll be using - the Pokon Seed & Cutting soil is self-regulating organic soil. Couldn't find the answer to this anywhere so I'm assuming the answer is no. Soil pH should be at 5.2-6.2 from the bag though. Any ideas? I have no idea what to make of this.