Hi @KarenMay,
Unfortunately, it would be extremely difficult to identify what is eating your plants based on this image alone.
Can I trouble you to take some photos of the actual plants? Are there any obvious signs of insects on the stems or around its base? Can you see eggs or scale deposits?
If you can't see any insects during the day, try having a look at night. A lot of the insects that are likely to have caused this issue would likely be hiding during the day.
Once we can identify what is causing the issue, I will recommend how we can fight the issue.
Let me know how you go.
Jacob
