do i remove just the leave part? or the branch of the leaf that attaches to the main stem too? which one? clarify!
Leaves start to yellow because the plant is using the nutrients in the leaf. I would suggest letting it fall off itself. However, if you must, wait until its about 75% yellow and clip the leaf. The whole branch if 75% of the leaves are yellow or it's below your canopy (if you're growing SOG style).