Gayle King believed Hayden Panettiere was “struggling” during their May interview, three months before the late actress’ tragic passing. The “CBS Mornings” co-host called Panettiere’s death at 36 “so, so sad” and “heartbreaking” during Monday’s show. “It was hard when she was here that day,” King, 71, recalled of chatting with the “Nashville” alum about her “This Is Me: A Reckoning” memoir. “When she was here in the studio that day, and I was talking to her off-camera, she was saying she felt that she was in a good place,” the journalist noted. However, King added, “She was still, clearly still struggling. To wake up to hear this news…