@mariac One place in the kitchen that I have found can easily harbor mold is the garbage disposal because it can spray food particles that stick to the walls that don't get washed down the drain. It took me a long time to figure that out.. out of sight.. out of mind. I take a kitchen dish washing long handled brush to scrub the disposal walls and make sure to scrub the rubber gaskets too. I didn't think about a lot of things like carpeting harboring dust and dirt because we have a house with all hardwood floors that we built because of my asthma. Dust causes allergies too and triggers asthma and accumulates everywhere. This link can explain a lot of places that mold can hide. Beware of harsh cleaning products too because the chemicals and fragrances can trigger asthma. We don't use cleaners that leave heavy fragrances behind.

Here is a link. https://molekule.science/11-common-places-check-mold-home/

Another supplement that thins mucous in the lungs is N-Acetyl Cysteine which you can get at a health food store or vitamin shop. It is an antioxidant and a pre-cursor to glutathione which is the master antioxidant in the body. I have taken it before and noticed my breathing get easier because of less phlegm. Here is a link about NAC.
https://www.healthline.com/nutrition/nac-benefits#TOC_TITLE_HDR_12

Thank you. Good luck on your detective work. Be well!