If the fish cost quite a bit I'd take them back and say you are afraid to eat any of them after getting so sick.
they may or may not be bad but I wouldn't risk it.

But if that was the only thing you ate all day that might have been part of the problem..or did you have any sauces or tartar sauce with it that might have been bad?

you might need to nibble on crackers or toast, applesauce, sip some soda pop or have plain rice til your tummy gets settled.