August wasn't a great month for most marijuana stocks. For that matter, neither was May, June, or July. Ups and downs come with the territory with investing in marijuana stocks, though.

But now we're in a new month and there's plenty to keep your eyes on in the ever-changing cannabis industry. Three top marijuana stocks that I think investors should especially watch in September are Aurora Cannabis (NYSE: ACB), HEXO (NYSE: HEXO), and CannTrust Holdings (NYSE: CTST). Here's what to look for with these three pot stocks.

Most of the big Canadian cannabis producers have already reported their latest quarterly results. However, Aurora Cannabis will be late to the party. By Sept. 15, the company is scheduled to provide an update for its quarter ended June 30.

Aurora gave a preview in early August for what investors can expect in its fiscal fourth-quarter results. The company should announce net revenue of between $100 million and $107 million Canadian. The midpoint of that range reflects a 59% jump from Aurora's net revenue in the previous quarter. 

Based on comments made by Chief Corporate Officer Cam Battley in the company's fiscal 2019 Q3 conference call, you can also expect that Aurora will report positive adjusted earnings before interest, taxes, depreciation, and amortization (EBITDA). However, the company didn't confirm this in its sneak peek at its fiscal Q4 results, so there could be a negative surprise in store. 

Maybe, just maybe, Aurora might also have some big news on the partnership front. The company brought billionaire investor Nelson Peltz on board in March to help line up deals with major partners outside of the cannabis industry. Aurora is behind several of its large peers in landing a partner but hasn't given any hints about the progress of Peltz's efforts yet.

Like Aurora, HEXO isn't on the same timetable for reporting its quarterly results as most Canadian cannabis producers. HEXO announced its fiscal 2019 third-quarter results in mid-June. Although the company hasn't yet set a date for its Q4 results, it seems likely that there will be an update this month.

HEXO should have some good news to report whenever its Q4 update happens. CEO Sebastien St.-Louis has predicted the company would double its revenue in the fourth quarter from the Q3 amount. The key to achieving that goal is HEXO's increased packaging capacity.

While HEXO isn't likely to be profitable in Q4 barring a boost from special items, there could be some confirmation that the company is on the right track. St.-Louis expects his company to achieve profitability in 2020, although he left some wiggle room by also stating that HEXO's investments in research and development could impact its bottom line.

HEXO already has a big partner, Molson Coors Brewing. But the company could shed more light on its discussions with a large number of Fortune 500 companies about potential partnership deals. HEXO anticipates adding at least one other major partner in 2020. 

CannTrust can't be accurately described as a top marijuana stock after its horrible fall in recent months. But the company is certainly a top marijuana stock to watch in September, if for no other reason than to find out if there are any other skeletons in its closet.

After starting 2019 with a bang, CannTrust imploded following revelations that it had sold cannabis that was cultivated in unlicensed grow rooms. The company's former CEO, Peter Aceto, was unceremoniously booted out as a result of the scandal.

The latest bad news for CannTrust came on Aug. 19. The Ontario Cannabis Store notified CannTrust that it was returning around CA$2.9 million worth of adult-use recreational cannabis that was cultivated in grow rooms that weren't licensed at the time by Health Canada.

It's possible that CannTrust could report its results for the quarter ending June 30 but don't hold your breath. The company already missed its Aug. 14 deadline. Perhaps the most anticipated update from CannTrust is related to its board's special committee that is reviewing strategic alternatives, including a potential sale of the company. There's no timeline for the special committee's report, however.