Page Six may be compensated and/or receive an affiliate commission if you click or buy through our links. Featured pricing is subject to change. Sofie Richie Grainge’s secret to luscious locks is now on sale. Just in time for Labor Day, shoppers can score up to 25% off Nutrafol products, including Grainge’s favorite postpartum hair growth supplement. (Plus, you’ll get free TSA-friendly gifts when you sign up for a subscription.) The model and brand ambassador previously praised Nutrafol for keeping her hair thick and healthy after giving birth to her daughter, Eloise. “I actually didn’t end up with any postpartum hair shedding,” she told…