Tufts Health Plan and a local company working on a more personal approach to primary care medicine are teaming up to open two new clinics for seniors in Medford and Hyde Park. The practices, run by Iora Health of Cambridge, will be available only to seniors who enroll in a Tufts health plan for Medicare patients. The companies plan to enroll 2,000 new patients at each of the two new locations. For Iora, the partnership will double the company's presence in Massachusetts. Iora has clinics in Dorchester and Burlington, among about a dozen clinics nationwide.