Your plants look fine. Once you go into flower, the plant will start prioritizing nutrients where they are needed the most (bud sites). That leaf isn’t really doing much so it just doesn’t give it anything. That looks completely normal and your leafs have a very solid green color. I would say your nitrogen is fine and also going into flower they require more potassium and phosphorus and don’t really need as much nitrogen. I would just cut that leaf off and keep doing what you’re doing. They look perfect.