S&P 500 ends down for a fourth day as valuation worries weigh

STORY: U.S. stocks ended lower on Tuesday, with the Dow dropping 1%, the S&P 500 losing roughly eight-tenths of a percent and the Nasdaq sheding 1.2%. Valuation worries hit big technology-related shares again, one day ahead of quarterly earnings from AI and market leader Nvidia, explains Kevin Mahn, chief investment officer at Hennion & Walsh Asset Management."I think many are questioning at this point in time how much longer can the AI infrastructure spend continue at its current levels. And they're right to question that. They're questioning the excessive valuations of some of these tech companies that are associated with the AI revolution in particular. [FLASH] Of course, Nvidia, Nvidia sits at the hub of the AI ecosystem as I see it. And it's so important to the psyche of investors around not only the stock market, but of the status and the health of the AI revolution overall."Nvidia's shares ended more than 2.5% lower. Fellow chipmakers slid, with AMD losing more than 4%, and Marvell and Micron Technology each falling more than 5.5%Among other movers, shares of Home Depot dropped 6% after the home improvement chain gave a forecast for full-year profit that disappointed and missed quarterly earnings estimates.Big box retailers Walmart and Target also report quarterly earnings this week.Meanwhile, the delayed September U.S. jobs report is set for release on Thursday, following the end of the record-long government shutdown.