Four days after Plug Power (PLUG -0.96%) got destroyed after raising concerns about its own ability to continue as a "going concern" last week, shares of Plug -- and also its hydrogen fuel cell rivals Bloom Energy (BE), Fuel Cell Energy (FCEL -2.80%), and Ballard Power (BLDP -2.40%) are taking off like rockets in Tuesday morning trading.

As of 11:20 a.m. ET, Bloom Energy stock is racing ahead 15.8%, followed by Fuel Cell with a 12.9% gain, and Ballard Power up 10.4%. But none of these fuel cell stocks are doing better than Plug Power itself, up an astounding 18.9%.

Why Plug stock is Power-ing ahead

This seems only fair.

After all, when Plug reported its big $0.47-per-share Q3 loss last week (57% worse than Wall Street had warned of, and also 57% worse than last year), shares of Bloom, Fuel Cell, and Ballard all got hit in sympathy as Plug stock got rocked. The fact that Plug blamed its losses on industry-wide "unprecedented supply challenges in the hydrogen network in North America" explains why investors would have worried that Plug's bad news would be bad news for other hydrogen stocks as well.

Today, however, these same stocks are all benefiting from some good news for Plug, as two big Wall Street banks cut their price targets on Plug -- but at the same time implying that the sell-off in Plug stock (and perhaps the other hydrogen stocks) has been overdone.

Granted, it might not sound like good news to learn that Wells Fargo, for example, cut its price target on Plug stock to $4 today, or that UBS cut its price target to $5 per share. But when you consider that Plug stock closed trading below $3.50 last night, both those price targets suggested there was once again some upside in Plug Power stock. They may also have implied that the other hydrogen stocks got sold off more than they should have.

Hydrogen is not out of the woods yet

That being said, I wouldn't get too excited about today's stock price rally in hydrogen companies. UBS's note did forecast significant underperformance in Plug's business ahead, warning that 2023 sales, which Plug promised would approach $1.2 billion, will probably be only $1 billion -- a 17% sales miss.

And according to a write-up on The Fly, the misses could get even bigger as time goes on. UBS is forecasting only $2.25 billion in 2024 sales -- not $3 billion as Plug had promised -- which means a 25% sales miss. And in 2026, the year Plug said it would breach $5 billion in sales, UBS is forecasting only $3 billion -- a 38% sales miss.

Granted, this is all Plug-specific bad news. But as we've seen over the past few days, as the bellwether for the hydrogen energy business, bad news for Plug can have an outsized effect upon the fortunes of other hydrogen stocks, too. Caveat investor.