Let me weigh in.

For one, Coco can and will dissolve given certain pH swings from acidic to basic and back. And if you thought those were bad, I've had TDS swings upwards of +1000. This is why I quit using meters and went back with basic stuff and DWC. I know the medium will break down eventually and that most of it is insoluble to plants without a suitable microculture (which I almost never run though I should,) and thus it will either buffer or interfere with your nutrients, depending upon relative levels and composition of breaking medium.

Runoff is almost useless unless you have initial input levels and output readings of equal volumes of liquid to determine how the medium is acting as a buffer/filter/storage medium. On top of that, it would *REALLY* help to get a soil NPK/pH testing kit. Saves my ass every year outdoors on some herbs (most other plants don't seem to care too much but rosemary and lavendar are apparently picky bitches!)

What they need to do is make a laser-based soil analyzer. You can easily determine what's going on by watching soil emissions, whether or not it has a healthy bacterial culture, whether or not enough oxygen is present for roots, ditto nitrates, etc.

Sadly that's probably another decade away, even with my research and failed attempts at building such things since high school, 13 years ago!