Katharine McPhee & David Foster Address Death of Nanny

Katharine McPhee and David Foster have suffered a devastating loss.

The couple shared an update after multiple outlets reported the nanny of their 2-year-old son Rennie died suddenly last month.

"It's been tough for her," David told Entertainment Tonight of his wife during their joint interview published Sept. 14. "Yeah, it's been tough. She's managing."

"Yeah," Katharine added. "Thank you."

Their caretaker Yadira Calito died after being hit at a Toyota dealership in California's San Fernando Valley on Aug. 9, sou…