Or, perhaps, eating at different restaurants once she moved? Perhaps something disturbing her sleep? Is she walking more or less? Is she walking through somewhere that uses pesticides or weed killer? Is the local grass watered with grey water that didn't get treated well enough?

If the cleaning crew bumps my work monitor an inch or two and I don't notice, I'll wind up with neck and back aches.

Commoner and closer things are more likely the explanation for something acute.

"Toxic waste" tends to be the culprit when you have weird disease clusters that are more chronic and take a long time to develop. "Toxic waste" that causes acute symptoms tends to be really obvious in multiple people.