Do they get full sun? Do you have any other info to give?
Some irises take a couple of years to get established.

Thanks for your response. These irises get full sun for at least 6 hours a day. I fertilize them in spring and fall. I have grown irises before that bloomed beautifully, and I am frustrated with these.

Perhaps you have been using a fertilizer that is too high in nitrogen? Lots of leaves but not much in the way of bloom stalks ? It might be helpful to have a soil test done by your Extension service.
Planted too deeply ? (I'm presuming that you're referring to bearded iris)
Crowded ?

They're probably too crowded. I'll thin them out.