Those probes are notorious for being pretty much worthless for ph, moisture, darn near everything they're supposed to give you an "accurate" reading on. They sell a ton of them to new growers. Get you a Blue Lab ph pen.
What brand coco are you using? Good brands come pre-washed and buffered and ph'd to 6.0 - 6.5. You should be more concerned with your watering/fertigating being ph between 5.8 to 6.5.
And again, I know from your other thread you disagree, but your coco is way too dry.
I just bought 3 different ones, thought it would be good for a rough indicator for trying to achieve that 30 percent moisture which you strongly disagree with haha
Did you watch them videos, if so what do you think about what they were saying, kind of makes sense to me as long as your using only coco, however if using perlite with the coco then this is actually not recommended, instead it’s keeping the medium more saturated as you say.
Plus, canna actually have another nutrient line called the cogr and this is more for a RTW system, when I explained to canna my irrigation set up they advised me this:
One thing to note is about the amount of run-off you plan to acheive using your technique.
CANNA COCO A&B is intended to be delivered to a substrate where the run off is minimal, and more managed via the moisture content needed. That way, there is time for the buffering of calcium and potassium to occur, where it becomes more favorable to flowering plants (higher potassium).
If you water to run-off each time, this accumulation is washed away with this run off. With your irrigation strategy it may be worthwhile looking at making use of the COgr line, typically used for a more granulated coco with high run-off amounts. It has a VEGA and FLORES version, to supply the change in ratio of NPK as demanded by the plant, which may not be acheived with a normal COCO A&B if you run to waste at such a high rate every irrigation.