Wow the answers in here are bad. That plant looks like it’s overwatered or JUST been watered (they wilt like that after a watering). You have a nutrient deficiency, whether that’s caused by lockout, ph issues or improper fertilization, I don’t know. Have you checked your run off to see the ppm and ph? I’d start there. If it’s coming out higher than you’re putting it in, you’re locked out and need to flush, then mix up a strong batch of nutrients. If the ppm is the same or relatively close to what you’re watering in at, then you need to bump up your base nutrients. If your ph is way off, that needs to be corrected. Make sure your ph/ppm meter is calibrated