Environmental was the first thing I thought of when this started with me.

We do not have well water, we are on city water.
Not sure about mold exposure, none that we are aware of.
Our home is 24 years old and we have been here about 14 years. It was checked for Radon when we bought it.
I have not been on any medication, unless it was an antibiotic or something for a sinus infection. I haven't had one of those in about 4 years. This round of steroids was the first and last med I had been on since then.
We only have our house sprayed once a year in the spring for yellow-jackets, and they haven't come this year yet.
Very seldom is anything dry cleaned.
We hardly ever go into pools, my daughter on the other hand…

My wife's B12 numbers are:
Vitamin B12: 427, Normal: 221-700

The only numbers that showed low or borderline for her were:
B6 29.2, normal 20-125
D25 31.6, normal 21-80 (I have now learned that 50 is more of an accepted normal)
Blood Creatine: 0.67, Normal 0.7-1.40
Blood Folate: >18, normal 2.8-18

Her docs didn't think these numbers were that important as they related to her reported symptoms. It surprised me, as I thought any number out of or near out of range would be worth looking at.

This is why I am leaning toward my sensations (or sometimes lack there of) as being more stress-related as I thought the odds of 2 married, otherwise healthy people coming down with some neurological issues within 6 months of each other just seemed to long to accept. Or, it has to be as you asked, something environmental.

Also, I should say that neither of our kids (15 & 8) have any issues like either of us have that we are aware of.