Here is what organic fertilizer does to coco. And no this isn’t septoria...it’s advanced nutrient lock / cal mag def among other most likely.
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Ends up locking out the plant because the ph goes through the floor. It got resolved by flushing with RO water, light hydro nutes (250-300ppm) and about 150ppm
cal-mag. Ph around 6.4 ppm total around 450. Brought coco ph from 4.8 to 5.7 over night.
The root zone WILL recover with a light nutrient flush.
I found my coco ended up unbuffered using organic nutes and very sporadic cal mag use. I didn’t know better so I lesson learned.
Are you measuring ph in the coco or nutes before feeding? Are you measuring the ppm/ec of the solution to know what is being fed?