not blooming this year

We had a bad winter; spring was cold and dry. Still, I'm shocked that so many iris did not bloom this year--
up to 75% in some beds, and irises that once were very reliable bloomers. Can this be just due to the weather? If not, what?

Too crowded, maybe ? Or have some trees grown to the point they are shading things more?

I've divided them faithfully; no trees around in area--plenty of sun. Not water-logged--soil here is sandy and it's been dry. Not giving them nitrogen-y fertilizer. Gave them some super-phosphate in early spring. Was hoping they were just late--but it's clear they're just not going to bloom. Miss giving them Cooley's iris spraing/fall formulae--Cooley's went out of business. ; (

Wow that is terrible. The only time bearded iris don't bloom for me is the year after they are divided. I just get foliage. Siberian iris sometimes don't bloom or bloom very sparsely if we have a very dry fall and I don't water them. They set the buds for the next year at that time. Hopefully you will get a glorious bloom next year.