Singer-songwriter Molly Kate Kestner releases her fourth single, “I Don’t Know.” Molly’s gritty, yet soulful vocals have been heard excelling on singles like, “It’s You.” On “I Don’t Know,” Kestner collaborated with cowriter/producer Starsmith (Ellie Goulding, Marina And The Diamonds, Clean Bandit) and cowriter Amy Wadge, best…