I've noticed black spots developing in my shower grout over the past few months. I think it's mold but not 100% sure. It's mostly in the corners where the walls meet. 😟

I'm a bit concerned because I've heard black mold can be dangerous. Is this something I can safely clean myself with bleach, or should I get a professional to assess it first?

Also, once cleaned, what's the best way to prevent it from coming back? My bathroom has a vent fan but maybe it's not strong enough? Any advice appreciated!