Funky tuna....Fukushima flavoring or did it just go off?

I've rarely had tuna since Fukushima, only occasionally opening a can I'd saved that was reaching the expiration date. I opened one of the last of my big cans a couple weeks ago, even drank the water- I used to eat tuna a few times a week, so you gotta understand after months of none, that to me, it was absolutely DELICIOUS!!

I bought a couple cans a week ago for a camping trip, figured what the hell- a couple cans and THAT'S IT. Never used them, opened one today, smelled a little funky but thought maybe it was just because I hadn't had tuna in a while. Then I ate it. And it tasted a little off.

Question-- seeing as how this is the first Fukushima tuna I've had, did I just eat off tuna? Or is there actually a slight taste difference? I've been burping like crazy since, but I don't actually feel sick...though I feel ashamed and saddened that I ate the dirty tuna and I promise to never do it again.