The first Monday of 2020 wasn't a particularly memorable one for either the market or a plurality of its top stocks. Both rose by fairly modest percentage figures.

Several companies, however, came down with a case of the Monday blues. Here are the whos, the whys, and the should-we-buy-it-nows of these two stocks.

Under Armour

Sports apparel star Under Armour (NYSE:UA)(NYSE:UAA) fell by almost 5% on Monday, and JPMorgan Chase unit J.P. Morgan is likely the reason why.

The storied investment bank relaunched coverage of the stock by downgrading its recommendation and lowering revenue projections for the company's fiscal 2020. It now believes Under Armour's stock rates a neutral, down from the previous overweight (buy).

Morgan also believes the top line will rise by less than 4% on a year-over-year basis. That's lower than the average analyst growth estimate of nearly 5%. The investment bank's analysis is based on lower-than-expected first-half sales and weak performance from discounted goods.

Once upon a time a hot stock considered a possible usurper of mighty rival Nike, Under Armour's appeal has cooled significantly.

Nike is a stiff competitor, as is European peer Adidas -- both have stepped up their respective games. While Under Armour's revenue in the crucial U.S. market has persistently slumped lately, those of Nike and Adidas have grown. An ugly and troubling accounting scandal that blew up last year hasn't helped sentiment on Under Armour, either.

That said, Under Armour is still a popular choice in both the professional and amateur realms of the sporting world, and the company still has some very high-profile celebrity endorsers (almost a necessity in this segment). I wouldn't be a buyer just now of the stock, but it's certainly cheap enough to track for signs of improvement.

A Carnival ship in port.

Image source: Carnival.

Carnival

Another Monday downer was cruise ship specialist Carnival (NYSE:CUK)(NYSE:CCL), which saw dips of 3% for both its New York Stock Exchange-listed stocks.

One possible culprit is an embarrassing pricing mistake that sowed some confusion over the weekend. Industry website CruiseRadio.net, in an article that was disseminated in other media, said that the company erroneously sent out an email advertising severely low prices for many of its upcoming cruises.

CruiseRadio.net posted a screenshot showing some prices as low as $100 for a weeklong cruise. The website said that one customer was told their attempt at booking a cruise at one of the advertised deep discounts would not be honored, as it was a mistake.

Carnival hasn't yet publicly commented on the matter.

If I were a shareholder, I wouldn't be too concerned about this. It sounds like an honest boo-boo, and there seems to be little customer/investor outcry about it. Errors happen in the corporate world, especially for sprawling and busy companies like Carnival, and they often recover and learn from such experiences.

Zooming out a bit, in my opinion Carnival is doing quite well. Baby boomers are in their twilight years these days, and many have money and time to spend on cruises. On top of that, younger travelers are getting bitten by the ocean travel bug; cruising isn't seen as quite the exclusive old-person activity it was once considered.

These trends helped power Carnival to record results in its latest quarter and fiscal year. Revenue has been growing lately, and management expects that dynamic to continue. Also, the stock's dividend yields a tasty 4%-plus. I feel like the shares are a buy these days.