I would recommend looking into defoliation for cannabis plants online. Some do it, some dont and both have their advantages/disadvantages, in my opinion. Personally I defoliate quite heavily as I believe they dont help the plant much after they begin to droop and yellow. The plant will drain the nutrients from the leaf but with plenty of nutrients readily avaible to my plants, I prefer to remove them to give the plants room to breath. It will also encourage more top growth which I believe pushes the plant to develop a larger footprint.
This is a highly controversial topic so i recomend thorough research.
Happy growing