Different metabolisms... The showing more chlorosis just needed more fertilizer or a hotter soil etc than the others.
There's no 'fattening them up.' No magic bullets. No secret tricks with profound effects. You either keep the plant healthy so it can meet its genetic potentil or approach it, or you do not. Everything falls short of "100%" no matter how hard you try. Your context is not doom and gloom. A little chlorosis is no big deal as long as the canopy can still function until th eplant fully ripens for harvest. Not all plants are the same robustness, but you cna treat these plants pretty shitty and still get an okay outcome. Numerous diaries show that playing out, lol.
The fact it has the most buds is probably related to the difference in nutritional needs.
give that one a higher dose... I'd just bump overall concentration 10-20% and see how it goes.. Some degredation of the canopy is tolerable late in life, but it should never die off. Make sure it can provide for the plant until the end. Just as some people look 50 years old at 75, and others look 90 years old at 50... not all plants age the same.
what happens over time informs you about the balance you privide -- enough, too little or too much. observe & adjust. there's only a couple times you have to make big adjustments due to stage of life. e.g. plant needs are a bit different when leaf growth and stem elongation ceases ("vegetative growth"). I drop my N about 30% or more, and then drop overall concentration further by mid flower, but this also depends on how i feed early on -- the plant will store up varying amounts based on what you provide over time... so everything you do from the start can make a difference of what is needed compared to someone else's garden.. learn how to observe and adjust to adapt to your local variables and processes.