For years, the Canadian athletic-wear brand Lululemon both pioneered and dominated the athleisure retail market. It turned workout gear into a status symbol, growing its international operations to 30 countries. But there’s trouble – a public battle with its founder, controversies over its marketing and a cratering stock price have all amounted to serious problems for the once-stalwart brand.Susan Krashinsky Robertson, The Globe’s retailing reporter, dives into the issues Lululemon faces, crunches the numbers of its financial outlook and asks what happens when a big brand loses its cool.