My one delphinium just started sprouting last week. I'm in central Jersey so maybe (fingers crossed) they aren't dead, just not awake yet.

I grow a bunch from seed every other year or so mostly as replacements, as they seem to be pretty short-lived, at least for me. Cutworms love them as well as slugs. They are pretty heavy feeders so as rich as your soil may be a good compost mulching may help. Did you dead-head after the first bloom and get a second? One thing that seems to help mine is giving them a good hard pruning and feeding after the second bloom as this seems to beef up the plant itself before winter. The biggest killer of mine is late fall/early spring sogginess so I try to keep the bases and soil as free of damp debris as possible. Hope this helps.
Oh, all but one of mine made it through fine and are already almost a foot high!

I had one for 30 yrs and someone told me it should be dug up and separated every 5 0r 6 yrs. This year it did not come back as strong as it had been so I did dig it up and replanted it. So far it seems to be doing ok. I learned something there. So hope this helps some of you. Tricia

I find that delphinium belladonna varieties are hardier and easier than the other kinds. They are not as tall but they are a beautiful iridiscent blue with several stalks, and sometimes rebloom after they are cut back.