Wall Street ended the week on a negative note, with the Dow Jones Industrial Average falling by triple digits for a second straight day and other major benchmarks suffering declines of as much as 1.2%. The latest news on the employment front seemed to be the catalyst for the downward move, as initial optimism about future U.S. economic prospects gave way to nervousness about possible responses from the Federal Reserve to rein in the economy before it overheats. Some poor showings from certain individual stocks also weighed on investor sentiment. Tesla (NASDAQ:TSLA), Delphi Technologies (NYSE:DLPH), and II-VI (NASDAQ:IIVI) were among the worst performers on the day. Here's why they did so poorly.

Elon Musk makes news again

Tesla stock dropped 7% after more comments from CEO Elon Musk made news. The electric car company's leader made disparaging comments about the U.S. Securities and Exchange Commission, suggesting that the regulatory agency has only made it easier for short-sellers to bet against Tesla's long-term prospects. Shareholders worry that coming just after Musk and Tesla had settled fraud allegations related to the CEO's failed attempt to take the company private, the comments could spur further litigation against the automaker. For many investors, Tesla's endless exposure in the news has merely distracted from the opportunities and challenges facing the company.

Red Model S driving on curving road with mountains in the background

Image source: Tesla.

Delphi deals with a departure

Shares of Delphi Technologies fell 13% in the wake of a major departure from the executive suite. CEO Liam Butterworth chose to step down from his role after less than a year of leading Delphi, and investors also reacted negatively to Delphi's reduction in its revenue guidance for the full year. Hari Nair will take over as interim CEO of the vehicle propulsion systems specialist, and with more than 30 years of experience in the auto industry, Nair should have the knowledge necessary to hit the ground running. Nevertheless, investors want to see more evidence of rebounding sales before they'll feel fully comfortable with Delphi's prospects.

II-VI falls in sympathy

Finally, II-VI stock finished down 8%. The laser maker declined along with several other players in the industry, as investors reacted to downbeat news from II-VI peer IPG Photonics. IPG cut its revenue guidance for the current quarter, blaming the recent imposition of tariffs for much of the fiber laser specialist's top-line shortfall, and earnings will likely trend toward the bottom end of the company's previously stated range. It's unclear how long tariffs might last, but as long as they do, the heavily trade-dependent laser industry could remain under pressure, hurting the prospects for II-VI and others.

Dan Caplinger has no position in any of the stocks mentioned. The Motley Fool owns shares of and recommends IPGP and Tesla. The Motley Fool recommends II-VI. The Motley Fool has a disclosure policy.