Wednesday was a positive day on Wall Street, though investors remained uncertain about the prospects for the stock market in 2019. Volatility was back, but key indexes managed to recover their losses from early in the session. Between the ongoing government shutdown and continuing worries about global macroeconomic and geopolitical factors, however, investors found it hard to build much positive momentum, and the major benchmarks only made small gains. As for individual stocks, Tesla (TSLA 2.99%), MyoKardia (MYOK), and Hologic (HOLX 1.57%) were among the worst performers. Here's why they did so poorly.

Tesla cuts prices as production slumps

Check out the latest Tesla earnings call transcript.

Shares of Tesla fell 7% as investors reacted negatively to a pair of news items about the electric-car company. First, Tesla said that it would reduce prices on all of its car models by $2,000 per vehicle in the U.S. market, raising concerns about whether demand for Tesla cars is holding up well. Moreover, Tesla's latest numbers on delivery volume were weaker than expected, with an overall 8% rise over the past three months to 90,700 vehicles falling short of consensus projections by about 1,300. With tax credits shrinking, Tesla's having to generate more of its customer demand without the help of subsidies, and that could prove difficult going forward.

Blue Model 3 on a road in front of a landscape of grassy hills and hazy skies.

Image source: Tesla.

MyoKardia's collaboration with Sanofi to end

MyoKardia's stock dropped 14% after the clinical-stage biopharmaceutical company announced that its collaboration agreement with Sanofi won't be extended after having expired at the end of 2018. The move returns global rights to candidate cardiovascular treatments mavacamten and MYK-491 to MyoKardia, leaving it up to the company to move forward with the lead candidates. Investors have been excited about MyoKardia's potential for a long time, but it's hard not to take Sanofi's decision as a vote of no confidence about the company's treatments.

Hologic deals with a downgrade

Check out the latest Hologic earnings call transcript.

Finally, shares of Hologic finished lower by 6.5%. The medical technology company received negative comments from stock analysts at Morgan Stanley, who downgraded Hologic from equal weight to underweight. Despite initially favorable expectations for Hologic's aesthetic surgical division, analysts believe that strong competition and potential regulatory scrutiny in some areas could cause the company to fall short of hopes. With a $5-per-share reduction in the analyst's target price on the stock to $39, Hologic will need to see business pick up in order to prove the Wall Street giant wrong.