To much nutrients, it was probably just a simply magnesium deficiency and instead of simply upping the magnesium you fried them with way to much -P-K, but in your case it was more -P- than -K. Yuck, that's really sad, I feel for you, but don't fret to much cause there is still enough life in a lot of those fans to still pull you in a half way decent yield. Anyhow, when using bottled salts, you shouldn't ever need to go above 1.2 to 1.4 ec or 600 - 700ppms to grow big, beautiful producing plants! For me, I never go above 500ppm(s) and that's including everything I put into my feeding mix!