Ive been checking my plants a lot recently and noticed some of them are getting a little limp. They are all in my windowsill getting 2-3 hours of direct morning and afternoon sun. They are just getting a little bit limp, as in the leaves and stuff. How do I make the leaves more compact, leathery, thick, and strong? Also, would any of you know why this might be happening? There is no browning or anything but its just that the plants are a little weakish. Thanks!