6.6pH and the pots don't drain, (organic grow) I only water about 5% -10% of the pots volume at a time and have been checking the pots soil daily with a (moisture) soil meter.
Honestly, despite what's often posted on mj forums, this is generally a frowned upon practice.
For more than one reason. One main reasons being accumulation of minerals and silts over long periods of time. Turns soils heavy as well.
Nothing wrong at all with a trickle out the bottom each time. It's sensible practice.
The big difference between this pot from the others is that It's mostly recycled soil from pots I had outside for a year or so.
Bingo^
The others look like they're over fertilized.. (dam Ocean Forest) so I'm really baffled by the one that's a pale green, came quick when I flipped 2 weeks ago. I've recently top dressed with some compost, EWC, and a little Craft Blend dry amendments. And before that I fed it some Neptunes Harvest fish n Kelp liquid fertilizer about a week ago.
You're right, it is just that 1 really.
(and it is) high in calcium carbonate.. one would think that the calcium could be the one nutrient causing the lockout, (but the pH checks out and the one plant of the six is ailing, why not the other 5 being watered by the exact same water?
I think it can all be attributed to aeration, honestly.
It's not calcium carbonate, it's not pH, it's not your input. (other plants are mostly good)
It's the plant's environment and your watering practices.
I'd be adding perlite to the ocean forest or recycled soil every time. And if you have been, add a little more.
Start watering until the point you get just a small trickle out the bottom. And periodically allow for more.