I am going to need more details or a photo to make a good guess but most often when all the flowers die in a bed it is lack of water. Too much heat, underground burrows from moles or voles and even someone using an herbicide on the bed by mistake are also explanations for why all the plants in a bed wilt and die. Don't give up. Dig into the soil and check for moisture. Pull out a dead plant and check the roots for damage or take a photo a leaf sample of a dead plant and bring it to a local nursery. You can learn something from all this and replant with fresh hopes for spring. Keep growing, Marianne Binetti