Runoff Questions

Was the plant healthy? All of these "flushes" are not good, if unnecessary. They are hard on the plant and should only be done in an extreme case. Sometimes coco is improperly buffered. If that's the case it'd be replacing Na and K at CES (what the coco "holds" onto) with Ca++ from fertilizer. This would not cause a rise in pH though. is your ph probe calibrated? those cheap things are trash anyway. Also, runoff is not 100% representative of what is in the medium Proper habits with soilless: Always fertilize with 1.2-1.5EC well-balanced, full diet (does not count what tap water add, just from fertilizer). Always get at least 10% runoff and don't let it sit in its piss. you need to get rid of that water. Wait for top layer to show signs of drying and repeat. Feel weight when it is "dry" and that's the best trigger for the 'next' fertigation. Also, if consistent about the weight loss, it will require the same volume of water to accomplish the task. You do not randomly pick a number out of your hat. You use enough fertigation water to get 10% runoff. Whatever it may be. pH-adjust what you add to 6.0, give or take a couple tenths. if this is not what you were doing, fix those habits first. Also, don't react in a huge way when you 'think' something is going wrong but the plant looks and behaving in a healthy way. i don't trust runoff readings. They are only useful if you learn what is normal when the plant is growing healthy, then use those readings as your baseline / norms. Things that differe from that are the warning indications.. again, don't go straight to flushing substrate over this unless they plants are showing severe issues, too. that should be the very last resort. If doing things right with watering habits and not overfeeding, it shouldn't take more than a slight adjustment to feed to get the plants back on track at any time. soilless is more scientific. you are the one adding 100% of the building blocks to the substrate in a known quantity, if you care to calculate it. It makes diagnosing problems easier and also makes refining your formula to the point 99% of all plants grow exceptionally well with little to no adjustments and very few surprises in that regard, ever. Anythng less than that is a failure to learn.

Something is off in your medium. Is it just composed of Coir like in your other question? Or are their other things mixed in? Maybe the other things are altering your PH, also maybe your PH pen need calibration. unless you using strips. great to have them as a backup for times of uncertainty. Most times when something is off in my medium the PH drops and does not go up. I also have a feeling the product your using for PH down may not be up to the task. A lot of users use Phosphoric Acid, some use other forms of a acid like vinegar or Citric Acid or even a solid sulphur product that will break down into sulphuric acid. Vinegar can kill off some microbes in the soil but its concentration should not be to high that happens, but long terms who knows. Best to start a diary and update as much info into it as you can. or I don't feel you going to get any realible answers as it will all by guesses not based on all the informaion.