When stocks fall in value, it can be a great opportunity for investors to scoop up some bargains in the process and potentially put themselves into a position to maximize the capital gains they can earn from buying low and selling high later. And when it comes to top stocks that are industry leaders, it can be even more appealing since they're good bets to rise in value over the long term.

Below are three top stocks that have declined in the past month that investors may want to consider buying today. Let's take a closer look to see why they've fallen in value, and we'll also consider whether they're good buys or if their share prices could be about to sink even lower.

1. Walgreens

Walgreens Boots Alliances (NASDAQ:WBA) is down more than 7% since it released its earnings earlier this month. The company has begun fiscal 2020 on the wrong foot as its sales and earnings came short of analyst expectations. With just 1.6% sales growth from the prior-year quarter, there wasn't much of a reason for investors to get excited about the company's performance.

The word "dividends" written above a piggy bank

Image source: Getty Images.

However, Walgreens is still a top stock, and it's a recognizable brand when it comes to retail pharmacies in the country. And while investors may be concerned that the retail business model is in trouble, it's far too early to count out this healthcare stock just yet. With the company considering providing drone delivery and offering more services inside its stores, it is adapting to changing customer preferences.

The moves could pay off, and there could still be a lot of potential for the company to capitalize on some new and exciting growth opportunities. With the stock trading around the lowest it has been since October, now could be a great time for investors to buy shares of the company and take advantage of the dividend, which is now yielding 3.3%.

2. Canada Goose

Canada Goose Holdings (NYSE:GOOS) is on an even steeper decline than Walgreens over the last few months. Its share price has fallen by nearly 7% so far in 2019 and 12% since the beginning of December. However, unlike Walgreens, Canada Goose released its quarterly results in November, and there haven't been any significant developments since then.

The one area that could pose a problem for the winter apparel retailer is China, where political unrest could cause issues. Last quarter, Canada Goose noted that the situation involving Hong Kong and China was weighing on the company and hurting its business. Unfortunately, there's no end in sight for that issue, and the stock could continue to plummet.

With retailers not performing well of late and Canada Goose's premium-priced parkas not being the easiest inventory items to move when consumers are facing cash shortages, there's likely more than a little apprehension in the markets surrounding Canada Goose's stock today.

However, with sales growth of 28% in its second-quarter earnings, the company has still been producing some strong numbers for investors. With the stock trading right around its 52-week low, it's another tempting opportunity for investors to buy on the dip. While the stock isn't cheap, trading at around 50 times earnings, like its clothing, it has commanded a hefty premium in the past.

3. Boeing

Boeing (NYSE:BA) has fallen a little more than 4% in the past month; its dip in price has been much more modest than those of the other two stocks on this list. News that the company would be suspending the production of its problematic 737 Max planes in January that sent the stock price downward. The planes have been out of service since two crashes occurred in March of last year, and the company is going to continue its review of the 737 planes for at least another year.

The silver lining here is that the planes could come back into circulation soon: Boeing is exercising caution in ensuring they are safe before passengers step foot on them again. Ultimately, it may be a non-issue a year from now, and it doesn't change the fact that Boeing is still a top aviation company -- one that generated $3.8 billion in profit over the past four quarters, despite these challenges.

Boeing is trading near its 52-week low, and it could be a good long-term option for investors who are comfortable hanging on to the stock while it sorts out the issues relating to its 737 Max planes. At a minimum, investors can benefit from the diversification the airline stock can offer as well as the income its 2.4% dividend yield will generate for their portfolios.

Which stock(s) should investors buy?

The issues surrounding Canada Goose and Boeing may not disappear for a while, and for those stocks, there's still danger that their share prices could continue to fall lower.

Walgreens, however, is only coming off an earnings miss, and it's the most likely of the three to recover soon. Without any geopolitical issues or problems with its products, the pharmacy retailer is the most likely of the three stocks listed here to turn things around this year, and that's why I think it's the stock investors should consider buying today. However, over the long term, all three could prove to be good buys.