I'd have to look it up, but last time that type leaf curl happened to me it was from low soil pH of around 5.4 causing a lockout, and I believe my runoff was around 1600-1800ppm
I can't recall exactly what I did but what I
would do is flush the medium well, and after it completely dried out I would starting feeding it balanced nutrients
with the correct pH for the medium at a moderate PPM