Investors in marijuana stocks such as Aurora Cannabis (NASDAQ: ACB), Tilray (NASDAQ: TLRY), and Curaleaf (OTC: CURLF) are having a good day today -- their first after four days of nonstop selling for some of these stocks. Through 12:12 p.m. ET on Wednesday, shares of Curaleaf are gaining 1.3%, and Aurora Cannabis is up 2.6%, while Tilray stock is leading the whole sector higher with a big 6% gain. The growing popularity of medical marijuana apparently is behind it all.