Now that I take a second look, looks to be happening to all plants.
- I remember reading you had already started a feed-water-feed routine. This isnt necessary until around your sixth node. I think all those nuted-feedings built up in your soil. Mine are still goin on the first 1/2 str I gave em back at their 2nd node.
-Also, I see discoloration in the middle of some leaves. This is a different deficiency. Probably due to wrong ph. I would look into getting a meter and either ph-up or down.