Detroit — Ford Motor Company is leading a drop in major U.S. automotive stocks this week because of disappointing results and doubts from investors about future performance.

Ford’s shares closed on Thursday at $11.16, down by 18.4%. This was the stock’s biggest daily drop since 2008 and the second-worst performer among S&P 500 companies. The decline happened because Ford missed Wall Street’s earnings expectations due to ongoing warranty problems.

Shares of General Motors (GM) and Stellantis also fell this week after reporting their results. Tesla’s shares, on the other hand, increased by 2% on Thursday after a significant drop on Wednesday.

The traditional Detroit automakers — Ford, GM, and Stellantis — were affected by industry-wide uncertainty and specific company issues.

GM closed Thursday at $44.13, down 5%, and has dropped 8.6% this week. Although GM exceeded Wall Street’s expectations for the second quarter and raised its forecast for the year, investors were worried about slowdowns in growth areas and concerns that the company’s earnings might have peaked.

Stellantis reported disappointing first-half results, mainly due to ongoing problems in its North American operations, according to CEO Carlos Tavares.

Stellantis’ NYSE-listed shares closed Thursday at $18.09, down 7.7%, and close to a 52-week low of $17.57 per share set in August.