Like most other large-cap growth mutual funds, American Century Ultra Fund has little to show in terms of returns this year. The $7.6 billion American Century Ultra was down 8.74% this year going into Tuesday. The market has been a challenge. The S&P 500’s 8% loss this year is the broad-market benchmark’s worst 10-trading-day start to a year in history, according to S&P Dow Jones Indices.