The U.S. stock market tumbled Thursday to one of its worst days since its springtime sell-off, as Nvidia and other AI superstar stocks kept dropping on worries their prices shot too high. Also hurting the market were questions about whether coming cuts to interest rates that Wall Street has been banking on will actually happen.

The S&P 500 sank 1.7% and pulled further from its all-time high set late last month. It was the worst day in a month for the index at the heart of many 401(k) accounts and the second-worst since April’s plunge after President Donald Trump shocked the world with his “Liberation Day” tariffs.

The Dow Jones Industrial Average dropped 797 points, or 1.7%, from its record set the day before, while the Nasdaq composite lost 2.3%.

Nvidia was the heaviest weight on the market after the chip company fell 3.6%. Other stocks swept up in the artificial-intelligence frenzy also struggled, including drops of 7.4% for Super Micro Computer, 6.5% for Palantir Technologies and 4.3% for Broadcom.

Questions have been rising about how much higher AI darlings can go following their already spectacular gains. At the start of this month, Palantir was sporting a stunning rise of nearly 174% for the year so far, for example.

Such sensational performances have been one of the top reasons the U.S. market has hit records despite a slowing job market and high inflation. AI stock prices have shot so high, though, that they’re drawing comparisons to the 2000 dot-com bubble, which ultimately burst and dragged the S&P 500 down by nearly half.

In the meantime, stocks outside of AI also fell across Wall Street as traders worried that the Federal Reserve may not deliver another cut to interest rates in December, as many had been expecting.