A Jetblue Airbus A320-200, registration N547JB performing flight B6-19 from Boston,MA to San Diego,CA (USA) with 126 passengers, was enroute at FL340 about 60nm northwest of Buffalo,NY (USA) when a number cabin crew reported feeling ill complaining about dizziness and headache, at the same passengers reported fumes/unusual odour in the cabin. The flight crew advised ATC cabin crew reported an odour from the aft galley and decided to turn around and divert to Buffalo where the aircraft landed safely about 30 minutes later. Three people were taken to a hospital, a number of passengers were medically assessed at the airport however no passenger was taken to a hospital. A replacement Airbus A320-200 registration N729JB was dispatched to Buffalo, continued the flight and reached San Diego with a delay of 6 hours. Passengers reported they were smelling an unusual odour and fumes aft of the wings, a good number of passengers complained about headache. Emergency services with detectors entered the aircraft after landing and checked the cabin. The airline reported the aircraft diverted to Buffalo due to crew members requiring medical attention. The Niagara Frontier Transportation Authority reported two cabin crew were taken to a hospital for dizziness. Airport police reported three cabin crew reported ill and were taken to a hospital. The airport reported two cabin crew and a pilot were taken to a hospital.