Bottom line.
You add, X amount of salt based fertilizers to coco fibers, which are grown to have high salt management potential.
Your plant consumes y amount of salts from the coco.
You add X amount more.
As you add more and more salt to the mixture, while the plant requires only so much, you will eventually reach a critical desalinization tipping point where the water in the coco is so loaded with salts it can't hold them all and you get precipitates. Before reaching that point the plant will suffer from the cation exchange. Consider the coco to have a high pressure of elements. The root cells work by osmosis and as the pressure outside the plant increases so will the pressure inside the plant in an effort to reach an electrical equilibrium. If you are pushing an improper ratio of nutrients for the ever changing needs of the plant this can result in deficiency from toxicity. Usually Magnesium.
In vegetative growth I find that damn near any feeding schedule, watering schedule, etc, works in coco. So long as you don't poison them or starve them your plants will do fine. I've had runoff over 4.0ec and plants that looked lush in vegetative growth.
In flowering growth I find that it is important to watch the runoff EC of the solution you are using and running the media more hydroponic until you have a thorough conceptualization of what the media contains and what your plants require. I'll say things like "never rinse with clean water" to new growers so they maintain a constant charge of elements. In my own garden I will use clean water on my vegetative plants, without runoff, to just let them continue consuming the salts present in the media.
Coco is a versatile media, about as versatile as they come. And cannabis is a versatile plant. Many methods will work ultimately but I think most new growers are looking for a foolproof method. Sure, feeding without runoff in coco might work for you, but you are in a group of about 5% of the coco growing public who employs such a measure.
I laugh at people that talk about "washing money down the drain." You could run 6 plants in a 5x5 with 3 gallon planters on most any nutrient system for under $200. If you wash out $60 of that total, and you grow 6 perfectly healthy beasts and pulling in an easy 20oz, you never find yourself complaining about runoff or being concerned about the cost. For a first time coco grower, save yourself the trouble and run a quality system, and get that runoff. My garden on Canna was 30%. Other gardens on different systems might not need more than 15% for the right EC.
After a few grows what I do is run my coco for 4 weeks or so just watching the plants and making sure they are happy. Things usually go fine. As I enter flowering for the first 3 weeks all I'm working on is dialing in the EC, increasing the PK+Mag levels (without really moving the N+Cal ppms) and building roots with Seaweed extracts ,which help keep internode distances shorter and buds tighter also. Watch the EC the entire time is absolutely vital to plant health. Just recently I had noticed a slightly high EC runoff reading. Two days later and I see the damage from just 1.85ec runoff when 1.25ec was used. A few leaves, nothing serious and easily resolved, but proof enough to me that in my garden the meter is king.
