Leaf identify

Symptoms: older leaves at base of the plants turn yellowish between the veins while the veins stay green.The green veins look like green stripes on a yellow leaf. Make sure there is no small dark structures on the leafs. If there is it's a fungal infection,growing in yellow tissue. From the pictures I don't see this.Your young leafs at branch tips look normal. The book and I say nitrogen (N) or Magnesium (Mg) deficiency. A deficiency is when don't got enough and a toxicity is you put to much nutrients. Add some Calmag with iron. Well hope best my fellow grower. Best advice never stop . Use everything as learning and pass on what you learn so we can have good medicine. BLESSINGS ON ALL U GROW AND HARVEST MY FELLOW GROWER!!!