Former J.C. Penney CEO Allen Questrom thinks it’s time for the department store retailer to find a new leader with the skills to drive top line growth. Penney’s current CEO, Marvin Ellison, unexpectedly announced this week that he will be leaving in July to join Lowe’s. Mr. Ellison has had some success paying down Penney’s debt and improving its supply chain efficiency, but has not been able to substantially raise revenues. The company’s share price has fallen 50 percent over the past year.