EC in input 2.4 runoff 3.9!

EC is a measure of the salt ions that are directly ready and available for uptake. 98% of plant nutrition comes directly from soil water solution. EC consists of two parts. Water and Salinity. (Salt ions) If you are adding 2.0 each watering then you must ensure your plant is utilizing the 2.0 before you add more. If your wet dry cycle drys the soil faster than the plant can uptake the salts then the EC spikes very high, as water evaporates, EC rises. Once the water is gone/evaporated we have like (for example) 1.5 EC worth of salts left in the medium..... now you add another 2.0 EC. Now you have 3.5. You are simply adding way more salts than the plant can utilize. The entire measuring of ec is far over complicated imo and one should , If they care to learn buy a EC metre for the medium itself rather than relying on semi complicated guesswork and a TDS metre pretending to be Electrical Conductivity. Its useful to know total dissolved solids you are putting in. Its great to know what total dissolved solids are coming out. Even better to know what's the real time Electrical conductivity inside the medium constantly and live day or night. Removes 100% guesswork of when to water and how much to feed. Failure to maintain consistent EC within a range will all but cripple the mass flow of a plant. When a plant loses the ability to take up nutrients via passive mass flow the energetic (ATP) demand to maintain nutrient uptake significantly increases, vast portions of vital energy will be used to uptake instead of biomass.

70/30 coco+perlite is a soilless medium. You probably aren't adhering to the 10% runoff every fertigation. This should never happen in a soilless medium. Buildup of nutrietns does not happen if you adhere to the 10% runoff waste water every irrigation, which should be fertilized every time, too. That's the basis of the primary benefit of soilless growing. Consistently maintaining a full spectrum of nutrients around roots that do not impede each other. feeding too high can still cause a toxicity, but it is 100% about the formula used and not buildup in the medium when you see it -- if adhering to the 10% runoff rule, religiously. 1) fully saturate with 10% runoff. Always fertilize with well-balanced diet. 2) wait for appropriate dryback and repeat. Don't over-complicated soilless fertigation. Any symptoms are solved through an adjustment to the formula. It takes all the guesswork out of what caused the problems you see. Something between 600-750 ppm will usually be enough to maintain health long-term. Most often you have to drop N quite a bit in flower and reduce overall concentration be mid flower. But, this heavily depends on your choices from the start.. fertilization is a culmination of everything you have provided since day 1... feed heavier early, needs less later etc... health of the plant is how you adjust and refine your formula. Easily avoid 99% of problems with a well-refined process. i have a steady formula for early vege through start of flower, then i start to reduce concentration in flower to avoid overly lush plants in mid to late flower. YMMV. Be systmatic. Make intelligent adjustments. It should be super easy to grow healthy plants within 1-2 grows using soilless growing methods. check out cocoforcannabis.com -- guides and articles are good information. avoid user-submitted. always find verification of any user-submitted advice, including this answer. There is a much greater proportion of bad information than good out there... often tied to seperating you from your cash.