Black on delphinium leaves

Hi there
Think that's just a bit of frost damage. I used to be a bit paranoid about my delphineums - they always seem to come up too early and of course frost damages them - I used to put buckets and plastic bottles and things over them! But now I just let them do their thing - some leaves get damaged - like yours - but they bounce back. In your piccy, the new young leaves look fine, so I wouldn't worry - I'm sure it'll be fine.