I'm sorry, dementia is horrible and most likely the major reason for the symptoms. Just remember that dementia patients can also forget to turn off the water and cause a spillage they don't remember, or fall down in the shower and spray the whole room with water, or simply forget where the toilet is and urinate somewhere. But nevertheless if it smells weird you should check it, one can have both dementia and mold in the house.

If you can smell that the house is bad for you then it would be easiest to just get her out of the damn house for one or two weeks, maybe to somewhere on the ocean, and see if her symptoms improve significantly.

Check her Vitamin D / iron / B12 levels and supplement with relevant cofactors. Doctors often don't check it here in Germany.

If she drinks tap water do one of the online water tests which checks both for bateria and lead contamination - both for hot and cold water supply. Contamination can be by old pipes or in the water boiler. If lead in water is high also tell the doctor.

If you have access to thermal imaging camera it is a very quick way to figure out water leaks in the wall or places of bad insulation. Maybe a shingle on the roof has moved and rain has been dripping into the ceiling. I bought one for ~350€ and didn't regret it.

As you mention the bathroom check the silicone sealings around the bathtub and see if they are broken and/or moldy. Maybe water leaks behind the shower because the silicone has a defect. Silicone needs to be relaced every couple of years, just rip it out and apply new silicone it is a DIY job with many youtube videos. Wear mask while you are in the house.

You can DIY hack a around-the-clock humidity/temperature monitoring with esphome/homeassistant so you can compare outdoor air vs. indoor air in several rooms and also calculate dew point temperature to see where/if water condensation in the walls occur. It is quite cheap and wifi-based but a lot of fiddling.

Good luck in these stressful times.

Thank you! I think I'll start with the water supply and air humidity monitors, vitamin D (supplementing), iron and B12 shows normal in blood tests.

> get her out of the damn house for one or two weeks Yes, this is my thinking too, I'm trying to solve the logistics of that as well, and hopefully we can do it soon enough.