Of note: Water lillies can absorb a lot of nutrients, but they need pre-existing nutrients to thrive. Otherwise they will languish, and you don't want to introduce nutrients just to get the lillies to grow. You may need a year or two to let the pond "settle".
You could put them in baskets or pots that keep good feed soil/fertilizer contained in them, which is how most water gardeners deal with it. Eventually when the nutrients increase, so will the lillies.
