Rivian fell as much as 26% to a record low and Lucid dropped as much as 14%, both in morning trading.
The two companies gave production forecasts late Wednesday that came in below estimates.
They said an uncertain economic outlook and high interest rates were hitting demand for EVs, echoing remarks from market leader Tesla and legacy automakers like Ford.
EV startups have been burning billions of dollars in cash in their efforts to develop, source and ramp up manufacturing of vehicles, hoping to be the next Tesla.
Their stocks have had a weak start to the year, with Rivian down 34% and Lucid down 12%, after a tumultuous 2023 when Tesla's price war roiled the industry.
Rivian is betting on the R2 sport utility vehicle set to be unveiled next month to compete with Tesla's best-selling Model Y crossover and attract customers with a smaller and cheaper EV.
Meanwhile, Lucid plans to start production of the Gravity SUV, later this year, with larger volumes expected in 2025 onwards.
