What eats/damages new iris shoots?

[Criscar]

Some creature in my pond has nibbled away both of the new shoots on my new Japanese iris. I have a lot of snails but to my knowledge none of them are plant eaters, and I’ve not had plant damage before. As far as I know the iris is toxic and inedible to the fish? Or is it possible to get a weird kind of melt on new shoots where they don’t appear diseased at all?