Wealthfront Inc.’s valuation was cut by about a third in its most-recent funding round after rising competition dented optimism about the start-up, according to people familiar with the matter. The digital wealth-management start-up, which amassed over $10 billion in assets under management since launching in late 2011, is now valued at around $500 million, the people said. They asked not to be named discussing private matters. The latest fundraising, which closed late last year, brought in $75 million. The last time the Redwood City, California-based company raised funds, in 2014, it was said to be valued at about $700 million.