Unknown holes and plants dying help!

[alfieplants]

We recently bought a pond plant and within a few weeks one of plants had been completely stripped of all green and the plant died, leaving behind dead twigs! Recently a couple of other plants in our garden have been attacked, a bleeding heart plant and rose bush. The culprit leaves holes in and around the leaves, slowly turning them yellow and then the entire plant and stem dies. (Images posted in comment)
Does anyone know what this might be, and what we can do to stop it?
Thank you!

 

[alfieplants]

 

[Anniekay]

Look around after dark with a flashlight for slugs and snails

 

[Oliver Buckle]

Just what I was going to say, because they are nocturnal they are the usual culprit if nothing is obvious. In the days of nasty metaldehyde slug pellets I used to go out with a torch and a bottle of hot water to drop them in, I don't mind using the modern iron based pellets so much.

 

[alfieplants]

Thanks both, will have a look for them at night. We had lots of snails and slugs earlier this year but could always tell they had been there (slime trails, some snails & slugs still there etc), but nothing this time points to them as the culprit, especially with something stripping the stem

 

[Oliver Buckle]

They do strip stems, a bit more tender than the inside I think. Lost one of my cucumbers to this, and they don't always leave slime trails. Good luck.