You've probably heard about this by now ... a woman in Alaska posted a photo of a trans woman in the women's locker room at her Fairbanks location -- accusing the company of allowing men in a space that she thinks should be exclusive to cisgender women.

The original pic appeared to show the trans woman in question shaving over a sink in the locker room, and the lady who took it ranted and raved on a video that went viral afterward.

In the aftermath ... her local Planet Fitness reportedly revoked her membership, and let the unidentified trans woman stick around -- who has continued using the locker room. Planet Fitness has also explicitly defended the transgender member, saying their policy allows people with certain gender identities to use the locker rooms that they see fit.

With that said, they also say people can't act in bad faith on this ... or they'll get booted.

Now, more photos of this trans woman have been taken and circulated in the days since all this first kicked off ... and as you can imagine, it's drummed up a lot of outraged reactions.

Specifically, a lot of folks on the right have been blowing this story up over the past week or so -- and they've been calling on people to cancel their Planet Fitness memberships nationwide ... and on its face, it would appear a good handful of members are doing so.

The reason that seems apparent ... PF's stock price has taken a somewhat big hit, and their market value has also plummeted -- with the stock going from $66 to about $56 over the course of 12 days or so, the amount of time that's passed since this firestorm has taken off.

As a result of the stock dip, their market cap has also fallen around $400 million -- going from about $5.3 billion to about $4.9 bil over the course of 5 days, starting last week.