Industry lawyers say mortgage lenders doing business in states within the jurisdiction of the U.S. Appeals Court for the 3rd Circuit might have to develop another regulatory strategy regarding third-party service markups in the wake of a ruling early this month. The court’s Aug. 4 ruling in Santiago v. GMAC Mortgage Group establishes a new view of markups in Delaware, Pennsylvania, New Jersey, and the U.S. Virgin Islands, which all fall under the 3rd…