700ppm isn't a light feed mate lol. It is by the manufacturers recommendations but honestly, nutrients companies know nothing about how to feed a plant. It's insane how useless feeding schedules are. It's about right for them now but up untill a couple weeks ago would've been a pretty fair dose.
You're best to find someone who uses them in the same media and ask them though bud. Theyll know best how-to sort it. That's a wierd media and a complicated pile of nutes. Im definitely leaning towards thinking the cocos went "hot" and the pH has went off. Guessing you don't have a probe so checking the pH and ppm of the run off would give a rough answer as to if that's the case. Wanna collect the first bit of run off that comes as that's the strongest and will give the best indication if something's not right.