Indeed, providing a detailed journal to a doctor about what happened around the time of the blackouts can be a very helpful diagnostic tool.
When you say "blackout" do you mean she remains awake but experiences amnesia (i.e., cannot remember events), or that she passes out/faints? These are two very different things, and clarity of what the symptoms are will also be important for the physicians treating her. Either one can be difficult to diagnose if the symptoms aren't actively occurring.
And, yes, any or all of those things could cause such symptoms, especially if she has a sensitivity or allergy to them. When she is at work, she should wear gloves when handling any cleaning supplies, and perhaps she can try living someplace other than the basement, and see if those resolve her symptoms. It's the only way to find out if either is the potential culprit, although, inhaling the fumes of some cleaning compounds could also be a culprit, but you could at least rule out a contact reaction.
But, of course none of those could be the culprit either. As DaleSpam pointed out, x-rays are not sufficient. They would only diagnose something grossly, structurally wrong, like a tumor. They aren't able to detect something like a spasm or blockage in a blood vessel, or a part of the brain that isn't functioning normally. If nothing largely obvious has been found in an x-ray, she should seek a neurologist AND an allergist (based on what you've shared of potential chemical/mold exposures) to investigate this in further depth.
And, if there's any chance of it, a quick rule out diagnostic would be a pregnancy test if you mean fainting when you say blackout (unless her doctor has already ruled that out). Sometimes it's worth considering the most obvious before running off to specialists for more obscure diagnoses.
