They might be planted too close together?

or too deep? The root should be underground but about 1/2 of the rhizome needs to be above ground. In the fall and spring sprinkle some bone meal or bulb food around them and scratch it in then water good.

There are numerous reasons why irises don't bloom, the most common ones being too crowded, too deep, immature or not established, and not enough sun.

Numerous reasons are explained at the FAQ at The Iris Forum: I have no bloom on my bearded irises. Why are they not blooming?

Sue