Nitrogen?

You look at the plant each day so if you see a trend in pigmentation (chlorosis / paling etc), then continue to keep an eye on it. At this point, it's hard to see anything, but the trending condition over time is what matters, not a snapshot in time that is an image. Need to see how it progresses before diagnosing. is it paling tip-in or between the veins (interveinal), for example.. is the damage low on the plant or high... where and how it progresses along with other information is necessary to diagnose with confidence. Slow-moving problems are okay. You have time to be patient and react accordingly. Doing the wrong thing only makes problems worse. Also, when you do come to a confident answer and see the effects you want from a reaction, consider small changes in your fertilization process used up until that point... avoid the problem completely next time. always good to track exactly what you fed and when you fed it... just because it looks awesome for a week or a month before doesn't mean it wasn't slowly progressing to the symptoms you see today. Slower progression = smaller adjustment needed.