Nationstar Mortgage Holdings (NSM) is in a strong industry group and boasts healthy fundamentals. But its chart shows poor action following a promising breakout. The mortgage servicer cleared a 37.30 buy point in huge volume on Jan. 7. But it's fallen for 10 of the past 12 sessions and as much as 9% below the entry. Investors should sell any stock that falls 8% from their purchase price. So those who bought at the breakout may need to cut losses