Kohlrabi and kale being chomped up

Help please,

My kohlrabi and kale leaves are being chewed to bits.

I started off putting down slug pellets. No good. I looked for caterpillars. No sign of them. Two days ago I covered them with fleece in case it is bird damage. I can still see the centre of the kale plants, so they are not totally destroyed. Not sure about the kohlrabis but they are still standing at least.

Any ideas please?

Anton