Chart-topping performerAdele is struggling to sell out her European shows weeks after postponing all dates on her Las Vegas residency through March on the advice of doctors because of a recurring health problem, RadarOnline.com has learned. The Set Fire to the Rain hitmaker is set to take the stage for 10 gigs in Munich in August after completing her Sin City residency this summer in June and insiders said that fans are concerned she will cancel. “Any updates soon? We need to plan and it’s impossible to do if we don’t have new dates. Leaving us in limbo is unfair,” one of which vented while an…