U.S. stock mutual funds fell for a third straight week, their first negative hat trick since May. The average U.S. diversified stock fund fell 1.52%, trimming its year-to-date gain to 0.11%, according to Lipper Inc. data. Funds investing in small-cap growth stocks fell the most among diversified stock funds, sliding 2.60%. The slide left them down the most for the year so far, 8.58%.