Perhaps the flushing has released much, much more dissolved salts that were previously trapped in the coir, back into circulation and causing the wilting due to a hyper salty environment, the wilting being caused by reverse osmosis.
Note, this is only a theory based on schoolboy chemistry and may be quite incorrect.
However, I do believe "reverse osmosis" has played a part/been the cause of it.
Cheers, Organoman.