Hi! I have a nice bunch of red bell peppers growing on my tower. The leaves are curling? What causes that and what do I do?

What is your biggest hydro gardening problem currently? mine is that my tomato plants are getting bigger than I ever expected them to be and they are, well, monstrous. And honestly the worst part is that everyone in my family is already sick of tomatoes from the last harvest.... lesson.... Grow what you will eat.... a lot of..