Could be a watering issue, could be too much of a certain nutrient...
I would recommend starting a grow journal...list all the details of your grow including lights, environment, grow medium, nutrient types and feedings.... This will help us understand what you have been doing as well as what the issue could be... also photos help
Pictures would help. If they're just droopy then its usually overwatering or a root bound problem. If they're droopy but claw shaped then it means you are over watering.