I came into the greenhouse on Monday to find I wasn't the only one stressed out this week. I'm working on finishing lengthy term papers for the end of the semester. The greens are stressed out because they are running out of nutrients. In some varieties stress is shown by leaves turning purplish, in others the leaves bleach to bright yellow. The tokyo bekana, kale, arugula and tat soi above are all brassicas that were first to reach harvestable size (Mizuna was as well, but I didn't take a picture of it looking stressed out). So, it makes sense that they would use up all their nutrients first. I am growing the greens in compost, which should provide all the nutrients needed. If I were growing these to eat, or for sale I would have harvested them last week before they got stressed out.