What happened In the first half of the Monday trading day, most of the stock market was up (the S&P 500, by the greater part of a full percentage point) -- but Aurora Cannabis (NYSE: ACB) was not. The marijuana stock was down by about 4.9% as of 1:23 p.m. EST. We can blame investment bank Jefferies & Co. for some of that decline. Image source: Getty Images. So what Citing "a post US election period in which at one point the ACB had gained 135%, not on fundamentals, but retail FOMO/hedge fund squeeze" (i.e. short-sellers feeling forced to buy the stock necessary to cover their positions at higher and higher prices), Jefferies declared Monday morning that "the valuation is too stretched" on Aurora Cannabis stock, and downgraded it to underperform (i.e., sell). As Jefferies analyst Owen Bennett explained, not only were Aurora Cannabis's fiscal first-quarter 2021 numbers awful (sales down 10% year over year, $81 million in net losses, and $93 million in cash burned), but the company moved to replace its lost cash by selling 20 million new shares, diluting existing shareholders in the process. Now what As bad as things look already, Bennett worries that they could still get worse. He sees it as entirely possible that Aurora Cannabis will continue creating and selling shares over the next 12 to 18 months, warns StreetInsider.com. And the more stock it sells, the more its shareholders' stakes will be diluted. 10 stocks we like better than Aurora Cannabis Inc.When investing geniuses David and Tom Gardner have a stock tip, it can pay to listen. After all, the newsletter they have run for over a decade, Motley Fool Stock Advisor, has tripled the market.* David and Tom just revealed what they believe are the ten best stocks for investors to buy right now... and Aurora Cannabis Inc. wasn't one of them! That's right -- they think these 10 stocks are even better buys. See the 10 stocks *Stock Advisor returns as of October 20, 2020 Rich Smith has no position in any of the stocks mentioned. The Motley Fool has no position in any of the stocks mentioned. The Motley Fool has a disclosure policy.Source