Plants need food as well as light and water; you are seeing the symptoms of an advanced nitrogen deficiency.
This would not have happened had you been feeding all along; however, it's late in the year to do anything about it except keep it from getting worse.
Give a bloom fert at this stage.
stinkyattic Reviewed by stinkyattic on . help! plants are about a month and a half into flowering and all of a sudden the fan leaves are beggining to yellow and fall off. the buds still grow out of the node where the leaf used to be, but i dont know if this is bad! what is the cause of this!? Rating: 5