nutritional excess or nutritional deficiency ( could it be excess of nitrogen)

I suspect pests. You can use Alfa-Boost or Boom-Boom Spray from Biotabs during this phase. If that's not enough, you can spray with a magnesium solution (I use Canna Mono Magnesium as needed and mix 2ml/l and spray them with it). Magnesium also acts as a foliar fertilizer and can be used during flowering (up until flushing). Wishing you good luck!

Ii get the pest thing. But it's just mag. If you've Epsom salt. A 250ppm feed or foliar spray will help. As if it was a pest, they attack indiscriminately. They don't say "hey guys let's attack in-between the vains to trick this guy into a mag def) but the radom marks, I do get why one would think its a pest. Idt so. Could be wrong. It just looks like a very light mag.

It looks like a pest and not a deficiency What are the black spots on the underside of the leaf in the last photo?