Did you, by any chance, split the clump last year? I ask because mine sulked for 2 seasons after I split them.

but they wont be in flower yet, isnt it a bit early? I split mine last year after they flowered in May. So I hope they flower.

Iris sibirica is a bit big for growing in pots, unless they are big pots. They are greedy plants and need both a lot of feeding and a reasonable amount of water. I am wondering if you mean sibirica and not another Iris?

Many thanks for tips. They didn't flower last two years! I have since split them. They are in large pots and I will feed and water them well and hope they flower this year. I shall include photo if they do. Again many thanks.