My green tea tastes fishy
A marine note that has gone past seaweed into something closer to fish, and it is not pleasant.
Likely cause
Usually water that was too hot for a delicate steamed green, which pushes fresh vegetal into cooked and then further. Sometimes it is age: the marine note is one of the first to turn as a Japanese green loses freshness.
Try this now
Brew the same leaf at seventy degrees for a shorter time. If the note goes, it was the kettle. If it stays, it is the leaf.
What to change
Cooler water and a shorter steep for steamed Japanese greens. Keep opened leaf cold, sealed and away from light, and buy in small amounts.