The ec of the coco is probably not nutrient related. Just ignore it. .18 is a lot lower than my tap water, lol.
The beauty of soilless is that ech time you fertigate with 10% runoff or more, you basically reset the nutrient solution around the roots and avoid buildup. So, any and all symptoms you see is 100% about you adjusting your formula to avoid those problems in the future.
I wouldn't just track EC. use a free app or website to calculate ppms of NPKCaMgS. If you know how much of each you feed, you can make more intelligent adjustments based on what you see. Within a grow or two if your first choice of fertilizers is a good one, you'll quickly have confidence to grow plants healthy from seed to harvest. Fertilizer isn't even on my mind when i grow. I try new things, but almost always revert back to my base formula. Systematically trying 1 or few things at a time -- like for a couple years i was trying higher levels of P and that was useless effort, so i stopped using the little P booster (0-46-0).
do the basics right and be systematic - whether coco or any other soilless medium. Always fertigate. Always get 10% runoff. While you may start with a reduced concentration with seedlings, it isn't necessary as normal soilless levels are safe - 1.2-1.5EC overall, not counting your coco or tap water.
You'll probably need to figure out vege phase - transition - bloom formulas, but again, if systematic, it won't take long to dial it in. I have my ppm break down in my recent diaries at various points.. think germ, flip to flower and the previous week or 2 weeks ago i shifted again... at FD 26 i cut feed by 50%, because of what i see in the plants and vege growth stopped, so it needs less going forward. a more drastic drop is something new for me, and hopefully it avoids overfed plants late flower. NEver a huge problem, but still want to learn to avoid it.