Veins yellowing

I've not come across this before, any ideas?

Honkeycorn, what book are those pic's from?

Iron deficiency. I'm pretty sure that is it, treat deficiency by lowering the soil ph to 6.5 or less. Avoid fertilizers that contain excessive amouts of manganese, zinc, and copper, witch inhibit iron uptake. High levels of phosphorus compete with the uptake of iron. Improve the drainage; excessive wet soil holds little oxygen to spur iron uptake. Increase root zone tempature. Apply chelated iron in liquid form to root zone. Leaves should green up in four to five days.

Str8 from my Marijuana Growers Bible!!!!

Anygood progress going on with that yellowing problem.

...I don't think its Fe....I dont know, I'm subbing to this thread....anyone else?

Bump...coz I really wanna know, veins yellowing first....