I understand that HP5 is probably the better choice right now, but don't discount Delta 400. I'm not sure what developing time you used, but if you used the same time as for HP5, your negative would have come out underdeveloped, which results in a loss of contrast and shadow detail. When you decide to develop on your own, try Delta again, and develop for the proper time.

You may not like it, but I think you should at least give the film a fair shake.