That's interesting SC. I haven't tried Coco myself but did see something that it was particular to certain things.
Coco is definitely a monster unto itself. All systems and methods have their pros and cons. Coco peat has this exceptionally high CEC as a result of growing in salt water. This capacity to retain a great deal of ions and salts is a two way street with the media. On one hand it allows for some really beastly growth rates. Maybe not as great as aeroponics or a properly dialed (modified)DWC, but probably the most vigorous of all the various medias available. On the other hand it also relies on the grower having some insight into the needs and requirements of the media itself because over-feeding can cause a cumulative effect that will stunt flowering later on. During Veg it is difficult to recognize the over feeding as the coco is building a buffer of salts.
With coco there are some rules growers need to abide by. Never let the coco go dry as this will allow the salts to precipitate which is all bad news when you water again. Also, always feed with run off to ensure that any excess has a chance to wash out. If a great deal of run off is not possible to drain then be sure to incorporate regular pH balanced waterings at <200ppm to wash out the excess and allow the plants to consume the rest. Don't over water an immature root system as the coco can stay very moist beneath the top inch for quite some time.
Coco does work best as a top feed drain to waste system, and the more draining you can do the better the plants will grow over the long haul. The structure of coco is kinda spongey, or... like a kush ball (lol, I just remembered those things) and this allows the coco to hold on to quite a bit of dissolved oxygen. The high levels of oxygen in the media help the roots stay healthy and allow a grower to water as frequently as they see necessary. Most growers water every other day, with some watering and some watering every 3.
Most growers in coco that do have a problem get it after maybe 10 to 12 waterings, sometime around 40 to 50 days into life and generally coinciding with the beginning of flowering. It is a matter of getting the media to the proper EC and then dialing back the feedings when most people are thinking they need to push their plants harder. Many new growers also make the mistake of including high PK supplements early in flowering. This can greatly upset the balanced CEC and the ratio of elements available to the plant causing a series of problems that become difficult to diagnose. As I buzz around the sick plant forums I see the over feeding of Potassium through a blooming agent, and the over use of Cal-Mag throughout life, contribute to a great deal of issues for people. Deficiency in coco is generally a result of toxicity of a salt unless the plant is very young and has yet to be fed.
Coco needs somewhere around 700 to 900 ppm per feeding (always exceptions to this given genetic variation), EC around 1.4 to 1.7. This leaves a pretty big margin for error if the plant needs 700 and gets 900 on several consecutive feedings. Without the proper amount of run off, over time, this excess can build up reaching a critical tipping point that appears suddenly despite the cause being a slow accumulation.
If you'd like to learn more about the science of Coco I suggest this:
http://www.cannagardening.com/node/1579/download