U.S. stock mutual funds were mixed but managed a slight gain overall in the week ended Sept, 11. The average U.S. diversified stock fund rose 0.08%, bringing the year-to-date gain to 5.83%, according to Lipper. Small-cap growth funds, the only diversified group still showing a year-to-date decline, rose the most in the latest week. They rose 0.83%, trimming their year-to-date decline to 0.59%.