Could the large gap in your vinyl plank flooring be harboring mold from water getting in from the improperly sealed tub nearby?

Hey guys, I could really use some help with a problem we’ve been having in our hallway. There’s this gap in our vinyl plank flooring that’s been bugging me for a while now. I can’t tell if it’s just dirt getting stuck in there or if it might be mold growing underneath. Gross, right?

The thing is, there’s a bathroom nearby with a tub that was never sealed properly. We hardly ever use that tub, but a few times we’ve given the dogs a bath and water has seeped into the gap. It’s got me worried about mold now!

I was thinking of filling the gap with caulking, but now I’m not so sure. What do you guys think we should do next?