The owners of a Sherman Oaks medical practice have purchased a San Diego hospital. Plymouth Health, a physician-owned practice formed by Drs. Pejman Salimpour and Pedram Salimpur, will pay an undisclosed sum for the 306-bed Alvarado Hospital Medical Center. The seller was Dallas-based Tenet Healthcare Corp., which announced the sale this spring as part of an agreement to pay more than $20 million to settle allegations that the hospital was paying kickbacks to doctors in exchange for patient referrals. Plymouth Health also owns Encino-based CareNex Health Services. Tenet also owns Encino-Tarzana Regional Medical Center.