The temp stays in between 75-82,What are temps in there. How you feeding em. What are they planted in. Are you going to defoliate?
And you've grown before so you're not making watering mistakes. So I would just do a lower defoliating. With soil my only moves are top dressing with worm castings..and adding Sulphur dust and DE as needed for pests. A lot of Fox Farms soil threads I've noticed have some issues with nutrients getting out of wack. They would have better advice. PH swings or lockouts can be an issue.
I have a few plants that have purple veins running up main stock u think that a ph problem or a deficiency problem?If you have a chicken farm nearby, go get a gallon of chix poop. It's almost 50% ammonia which is nitrogen. Very lightly top dress.
You are in flower, The plant is genetically designed to slow the uptake of certain nutes at specific points in their lifecycle.
When you go to flower, your nitrogen is cut back to help the plant transition to flower. Afterwards, this causes a shortage.
I would de-fol from the yellows on down.