Listen equanimity,mild thrives in damp,so ur gona have 2 find a way 2 keep that room warmish.is it a normally a cold room during the winter.maybe u should look at removing top half of soil with the mold on it,an replace it with new soil.but lack of heat has 2 be triggering that hold 4 u.hope u get it sorted.if that's usually a cold damp room during winter,then there may be damp sitting in the corn or of the walls that u can't see.so if that's the case,remove all plants from room,an clean every inch of the walls plus ceiling.