My experience is with a different brand of nutrients and I don't do PPM or EC. Once you get out of the seedling stage, life is easier. You cannot give a plant in coco too much water, but you can overdose it with nutrients. Start with a half dose. If they can handle it, go full strength. Your plant will tell you what it wants.
Ignore the Solo cup reference, and some folks do not do runoff in coco. Nothing wrong with it, it just isn't necessary. Make sure the water gets to the bottom of the cup.
From the webpage you posted, here's what I'm talking about.
4.) Start Seedling-Strength Nutrients
After seedling grows first set of “real†(serrated) leaves, water with nutrients at normal seedling strength, and add a regular dose of Cal-Mag (Calimagic). Keep giving water until you get about 20% runoff ut the bottom of the solo cup. The first set of leaves are round, but the second set are serrated and pointy. Once you see those leaves, it’s time to water your seedling with nutrients.
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