What size of Cordylines did you have? The larger ones can re-sprout from the base. I lost 2 in 2010 (red and green) as the soil was soaking wet after the bad snow and frosts. The ones that survived locally all had good drainage (lots of grit added around them). If you are buying new ones I suggest amending the soil to make it free draining as possible. General fertiliser and pellets is all that they need. if you are feeling rich then Palm Booster is a seaweed based feed that is supposed to be good for them and palms.

Hi Googie, I would prepare the planting places, by incorporating garden compost, well rotted manure, and a hand full of blood, fish & bone, or bone meal, after that they will not need feeding for quite a while, but if the ones you lost were bigger than the replacements you have bought, and the reasonably mild winter we have just had killed them, why would you want to replace them, they wont even be as hardy as the ones you had, and you could end up losing the replacements as well, I would think about replacing them with something a bit more hardy, eg, phormium, especially the all green ones, yucca, or if you want a hardy palm, trachycarpus fortuneii, but I certainly wouldn't replace with the same again, but it's your choice, Derek.