Why are my calla lily potted plant blooms curled and not opening?

Without seeing the plants it's difficult to tell what might be happening. It sounds as though you're giving the plants the care that they need with lots of sun and moisture. Are there buds that are not opening, or are these the blooms that were on the plant when you purchased it? When a particular bloom has finished blooming, it fades and rolls up as seeds form. Perhaps this is what is happening.