Amaryllis Did Not Bloom This Year?

My amaryllis have been outside in a large planter for many, many years. During all of those years they have bloomed red each year at or near the beginning of spring. I am in So. California. This year there was not a single bloom on all of the 14 bulbs in that planter. Is this normal after so many years? The leaves are full, green and healthy. They get watered when it rains, which is not often here, and maybe once every two weeks or so. They are definitely not over watered.