South Korea’s stock market crash quickly took the shine off one of this year’s biggest AI success stories: the rise of Samsung Electronics and SK Hynix to the trillion-dollar club.

Buoyed by the global artificial intelligence boom, both memory chip giants crossed the $1 trillion market capitalization threshold in May, as investors flocked to companies expected to benefit from growing demand for AI infrastructure.

But since then the rally has reversed dramatically and both companies have left the club.

On Thursday, South Korea’s benchmark Kospi index closed down 1% and is about 40% off its late-June high.

Shares of Samsung Electronics closed down 1% after reversing gains that followed better-than-expected second-quarter results. Samsung reported a 1,800% rise in operating profit to 89.5 trillion won, or about $62 billion, beating analysts’ expectations. The stock is 45% below its high last month.

Meanwhile, SK Hynix shares closed 6% lower and are down about 56% from their June high. The latest drop came after another record quarter for SK Hynix, as operating profit rose 557% but fell short of analyst expectations.

Samsung Electronics and SK Hynix are now worth about $924 billion and $707 billion, respectively, according to LSEG data.

The change is especially striking in the case of SK Hynix.

SK Hynix, once largely considered a maker of cyclical memory chips, has transformed itself into the leading supplier of high-bandwidth memory chips for AI accelerators, jumping into the ranks of the world’s most valuable technology companies.

Earlier this month, it capped that rise with a $26.5 billion Nasdaq ADR offering, the largest sale of U.S. stocks by a foreign company. The offering was priced at $149 per ADR, but U.S.-listed shares have since fallen below that level, highlighting how quickly enthusiasm for AI chip stocks has cooled.

The pullback has also exposed risks posed by South Korea’s rise in single-stock leveraged exchange-traded funds, which have magnified the slowdown as retail investors unwind their leveraged positions, adding momentum to falling stock prices.

South Korea already this month suspended new listings of single-stock leveraged ETFs and on Wednesday promised additional measures to stabilize the market, including limiting retail access to the products.

IG market analyst Fabien Yip said the measures should ultimately help restore more orderly trading.

“New government limits on retail leveraged ETF allocations may accelerate short-term selling, but should support a healthier and more rational market once deleveraging is complete,” Yip said.