About 6 months ago I began to notice a very strange smell in one of our bathrooms. It is like nothing I've ever smelled before, kind of sweet and a bit yeasty. Since I first noticed it it's become stronger and kind of drifts out into the attached bedroom.

I've checked all the cupboards and drawers for any sources, smelled the sink drain (there is no tub) the heat vent and the fan vent in the ceiling without finding any obvious source. I have had a plumber in who checked under the toilet in the crawl space but couldn't see anything odd.

I am not sure what to do about this. Who to call in to check this further... a mold expert? (there is a sign of some leaking in the soffit at that corner of the house, over flow from the gutter when the down spout plugs) a builder? Contractor?

Thanks for your consideration.