Originally Posted by lh66
There must be some place that is leaking. It may be best to hire a professional to find the source and fix this
It doesn't need to be a leak! Very often it is condensation forming on a cold pipe in winter, that drips down making whatever wet... then mold grows.
However, you do not expect that in a bedroom wall, a small patch is usually down to condensation, caused by cold wall, lack of insulation, lack of warm air circulation.
With most of this type, the mold dies during the warm days of summer.
Perhaps we will get an update later this year?