For every one else ,,,,,,,
Simply watch your plants and you'll see it, leaves with red stems are sinks, non-red stems are sources (the solar panels) the defoil experts know to remove the sinks LOL (adding that cause this is a defoil thread) The number of sinks you see on a plant is directly proportional to the amount of nutes available in your medium. The plant stores nutes in preparation for winter, it is genetically encoded to do so and it only stores what it needs. When the leaves start to yellow, whether from the natural fade at the end or from an N def you will see that the red stemmed leaves are the ones it pulls from. All ya gotta do is watch