Maybe it’s due to iodine, not omega 3s.
Nah it’s the mercury.
Could be both, as both are materially deficient in modern settler populations, including nursing moms.
I'm a consumer of a higher dose fish oil. I'd prefer to get it all from actual seafood, but that is dangerous in the modern world, due to the modern marine toxins problem, principally mercury.
The fish oil supplement market is a separate minefield.