Molds can be tricky since they will grow in places you can't get to.
The areas you can get to can be treated with a borax solution which will inhibit both molds and fungi. If you have enough humidity to grow molds, you have enough for fungi to sprout.
Dehumidifiers are very helpful for reducing mold.
Check the attic to make sure you have enough ventilation up there, that goes a long way and if it is an old building, that might be one of the issues.
Air flow needs to go from soffit to peak, lots of times in old houses, they add insulation in the attic but forget to leave the soffit vents uncovered or there aren't any in the first place.
You need to do a complete inspection, foundation vents, soffit vents, gable peak vents, all
should be there and the more humidity you have the more vents you should have.
I put vents every 8 feet (foundation and soffit, gable peaks and ridge vents too) here in Arkansas, we have high humidity most of the year.