That's a small plant, 600 + ppm? WOAH!!!
Bump that down to around 250-300 if your pure coco. Coco has a lower CEC than peat. But it still holds onto nutrients. Flush your pot with pH adjusted water. Or very low nutrient charged water, pH stabilized at 5.8
Flush 3 times the volume of coco. Right before you finish the total volume of flush solution, capture 1 cup of the final amount if liquid to drain out of the pot. This is your sample to test pH and PPM. EC is more accurate as it doesn't recognize fine particles, possibly from your substrate. Only the electrical conductivity.
Once your in an exceptable range as per the plants stage of growth and age, allow the substrate to dry for a day to rebound the plant. Then as needed adjust nutrient strength. There's nothing wrong with running the same EC for longer, you can always increase it easily. Reducing it is the shit part. Less is more! Also by maintaining a higher EC within the plant tissue than the substrate, this keeps the plants constantly uptaking elements, always hungry for more.
Less is more!
