If you're a bargain-hunting growth investor, you might want to browse last month's Nasdaq-listed laggards. Although the Nasdaq Composite (^IXIC -0.33%) itself logged a 4.1% gain in July, a bunch of its individual listings didn't follow suit. A few of them -- even some of its most popular large caps -- suffered double-digit percentage declines instead.

Or, perhaps these particular tickers tumbled for a reason and still have more downside in store to dish out. Let's take a look.

What went wrong for whom?

There's no need to belabor the point: Last's month's biggest losers among the Nasdaq's largest names are Enphase Energy (ENPH 4.69%), Willis Towers Watson (WLTW 1.18%), and SolarEdge Technologies (SEDG 3.45%). These stocks lost 9.4%, 10.3%, and 10.3% of their value in July, respectively. (Dis)honorable mentions go to Ryanair Holdings (RYAAY -3.25%) and American Airlines (AAL -4.06%), which fell 7.3% and 6.7% last month in spite of a turnaround effort late in the month.

^IXIC Chart

^IXIC data by YCharts

In most cases, these kinds of setbacks aren't in and of themselves reasons to buy a stock. Such weakness is often just a reflection of fundamental trouble, after all.

Take Enphase Energy as an example. The bulk of its July stumble took shape in response to its third-quarter guidance, published in conjunction with its second-quarter results. Although sales of $711.1 million were up 34% year over year and per-share earnings improved to the tune of 37%, sales fell short of estimates.

Guidance for the quarter now underway was also lackluster, suggesting demand for solar power equipment isn't living up to expectations. SolarEdge hadn't yet reported last quarter's results but fell all the same on worries that it too is running into a demand headwind.

Shares of London-based insurance company Willis Towers Watson nosedived for a similar reason. That is, while revenue of $2.2 billion was up 6% and better than anticipated, earnings of $2.05 per share were down 12% year over year, falling short of expectations.

As for Ryanair and American Airlines, the setbacks are ultimately rooted in the same cause. Ireland's Ryanair downplayed last quarter's huge earnings growth by warning investors that the current swell of demand -- and pricing power -- might not persist to and through the end of the year. Likewise, while American Airlines' record-breaking top line of $14.1 billion was 4.7% better than the year-ago figure, it also offered guidance the market interpreted as being subpar.

The question remains, though: Are any (or all) of these sell-offs a mistake, and ultimately a buying opportunity rather than a red flag? It depends.

Don't ignore the same, repeated warning

For the record, while you should be looking to buy stocks you want to own while they're down, just because a stock's down in a particular calendar month doesn't inherently make it worth owning. Some companies are trainwrecks every 12 months of the year. Sometimes more than one month's worth of selling is in the cards. Sometimes, such a steep sell-off is a mistake that will be corrected sooner than later. There's always more to the story.

This particular month, with these particular stocks, however, there are bigger-picture themes to consider. Of these laggards, two different airlines loosely pointed to a looming headwind. And of these same laggards, two different solar power technology stocks are signaling slowing uptake of their products. What you don't see is that solar panel maker SunPower recently dialed back its full-year earnings before interest, taxes, depreciation, and amortization (EBITDA) guidance, as "Demand in the second quarter has weakened more than expected in the Southeast and Southwest."

That warning certainly underscores Enphase's lackluster expectations.

Oh, and since the end of July, airline JetBlue reduced its full-year profit forecast, citing (among other things) waning demand for domestic travel services. SolarEdge also served up revenue guidance of between $880 million and $920 million for the quarter now underway versus analyst estimates of $1.05 billion, sending the stock lower in response. 

A couple of clear themes are starting to firm up here. 

The point is, take these companies' worries at face value. None of them want to upend their stocks. But they're doing so anyway, and they're not alone when they are. It's conceivable these wider, bearish narratives could start taking on a life of their own -- even if just temporarily -- further fanning the selling flames.

Make a point of taking a step back sometimes

Veteran investors innately know this, of course, even if they don't overtly know they know it.

If you're a new investor feeling a little overwhelmed by the concept, though, don't be. It's not really all that complicated of an idea. In fact, it's a fairly simple premise that can make you a much better investor.

That is, most industries' companies (not to mention their stocks) move in a herd. They're all addressing the same customers, after all, under the same conditions. They're often using the same technology, know-how, and supply chains. If one or two of them are saying the exact same thing, there's probably something to it.

Continue to be company-specific about your picks, looking for unique edges and competitive advantages. Just don't forget to take a step back every now and then and assess the bigger picture. There's a lot of value from that perspective as well.