Subprime lenders told a generally good profit stories during the second quarter, but competition is continuing to eat away at their bottom lines. A case in point is NovaStar Finanical. The Kansas-based real estate investment trust reported $37.9 million in second-quarter net income, an 11 percent year-to-year rise. The company noted, however, that “tight spreads” on new production have hurt profitability while highlighting the importance of a high-volume, low-cost business model. …