If some older fan leaves appear to be extreamly dark, or slightly waxy, you may be overfeeding.. The downward leaf curl and narcosis,(dead tips) would indicate to me to much (n). Yor plants are fairly far along so do not panic. You could try just using water for the next while, and if they worsen, try leaching. I would also consider using something other than schultz, those numbers are extreme, and it is not a quality product.