Call a mold pro;)

If you have some small spots of mold, wash then off with clorox wipes or similar product. If there is no damage to the paint then just try to keep the bathroom better ventilated after showers and baths. Run the fan and leave the door open until the bathroom is no longer humid after use. Make sure all people using the bath are doing this. Also keep the room as dust free as possible. The dust gets wet from humidity and makes a great place for mold to grow.

Aaron, what is up with that?? I just saw this. My question is...Is the mold growing through and actually coming from somewhere else or is it just appearing on the surface? On the surface, put a timer on the fan and make sure it's big enough for the space. What other rooms does that bathroom butt up to? You're in New England....is it showing on an outside wall first? shoot me a pm on FB