Small bit of extra feed should do away with that.
But even saying that. Be careful it looks like your plant is in or very near optimal conditions
Sometimes leafs lower down will just get eaten or bypassed to support other growth.
But more than likely it'll just a slight N def that happened in the push before pre flower.
If you see any leafs higher up go yellow and keep going yellow then you have an issue.
It all looks good to me.
Good luck.