Home prices in Southern California hit a six-year high in March, but sales have begun to slow due to a lack of demand, according to San Diego real estate data firm DataQuick. The median price paid for all new and existing houses and condos sold in the six-county region last month was $400,000, nearly 16 percent higher than the $345,000 median price a year earlier. That price is 4.4 percent higher than the prior month and represents the highest price since February 2008 when it hit $408,000. However, the pace of buying has slowed. Some 17,500 new and existing houses and condos were sold in March, up nearly 26 percent from last year but down 14 percent since February. “Southland home buying got off to a very slow start this year, with last month’s sales coming in at the second-lowest level for a March in nearly two decades,” said DataQuick analyst Andrew LePage. LePage said that the slow-down comes from both low inventory and rising prices, which have removed some prospective buyers from the market. Kahn Media Inc. was hired to represent Nitto Tire U.S.A. with public relations and marketing product debuts, the Reseda firm announced Thursday. Nitto Tire, based in Cypress, will work with Kahn Media and its Long Beach digital agency Cie Studios to increase sales of the Japanese subsidiary company through more brand visibility and promotion at motorsports events. Nitto is owned by Toyo Tire & Rubber Co. Ltd., in Osaka, and makes tires for street cars, trucks, and the off-road, road racing and rock-crawling markets. “Nitto got its start in the United States by offering the best possible product to enthusiasts, and grew its brand from there,” said Kahn Media founder and President Dan Kahn.