Lambs ears (Stachys ) tend to grow like weeds so you can thin out and do whatever they always come back. As for the holes I'm not sure that's snails as they tend to eat from the sides, I'm sure someone will come up with a solution.

Might be slug damage or earwig damage, so slug pellets might help, but to be honest, at this time of year, I'd ignore it. These plants tend to look terrible by late winter, particularly if there's been a lot of rain about, so the time to thin out and remove untidy or damaged leaves is spring, as it starts growing again.