Hedge funds that piled into real estate investment trusts are hurting the companies on their way out. REITs that have had a relatively large portion of hedge fund owners are struggling with declining stock prices. NorthStar Realty Finance Corp. is one of the two worst performers this year in a Bloomberg index of 41 mortgage REITs, with a 39 percent decline. IStar Inc. has dropped 25 percent, Colony Capital Inc. has fallen 19 percent and New Residential Investment Corp. has slumped 10 percent.