Deficiency: Nitrogen is the most common nutrient deficiency. The symptoms include slow growth. Lower leaves cannot produce chloro- phyll and become yellow between the veins while the veins remain green. Yellowing pro- gresses through the entire leaf, eventually caus- ing it to die and drop off. Stems and the leaves' undersides may turn reddish-purple, but this can also be a sign of a phosphorus deficiency. Nitrogen is very mobile, and it dissipates into the environment quickly. It must be added regularly to sustain fast-growing gardens.
Progression of deficiency symptoms at a glance:
Older leaves yellow between the veins (inter- veinal chlorosis).
Older bottom leaves turn entirely yellow.
More and more leaves yellow. Severely affect- ed leaves drop.
Leaves might develop reddish-purple stems and veins on leaf undersides.
Progressively younger leaves develop inter- veinal chlorosis.
All foliage yellows and the leaf drop is severe.
###Credit to Marijuana Horticulture by Jorge Cervantes
Hey, im a newbie like u so don’t believe in me so much, however, according to the book im reading, it could be Nitrogen deficiency. I wish i could upload an image here so instead i copy-pasted here and upload the pic(which include the diagram) in my incompleted diary in case u wanna take peek.
Good luck buddy!