I would hit those with 28-0-0 at 150 ppm, if you can do it. Yeah, just checked the picture. I am working on rooting in young clones, and they get like this. When they do that, they need more Nitrogen in the flowering. The sign here is transporting of N, from the bottom to support the flowers. That reduces the photosynthesis, too soon.
So, N for sure. Here is my definitive source for other deficits and seems to work for me.
Nutrient Knowledge Article's Merged
Purple is a flowering trait, also, in some strain. In others it can be over water and severe stem shrink. But that was the first thing I checked. Your upper stalk is not purple and thin. Not with that fine leaf set and good green up top.
Do you have some lawn food? Or what do they use in organic for N? Bat guano? Chicken manure?
You need to not do nothing, but not do too much, here. Do no harm. Just ease into a more balanced plant food. I use organic 16-16-16. MaxSea or I use Sea Grow, seems the same for less. Who knows? I don;'t want to make Uncle Buck seem like a nice guy or anything but he turned me on to it.
I might add some Cal/Mag in early rooting. I add Silica for strong stems. And then only the PPM changes. Same stuff start to finish, vary the PPM.
So, even if you use Scott's Super Grow with Iron in a 150 ppm water solution that will do it.