The main reason for a plant to bloom is to create a seed so that the species will live on. Sometimes a plant does not have much energy so it will produce a bloom but not have enough energy to produce any stalk at all. Usually a plant that is lacking energy will produce short stalks.
It may be that they have suffered environmental stress to the point of thinking they are in danger of dying and produce a flower in order to make sure they do not go extinct. I know this sounds like i think plants worry about what's in fashion and who to vote for....

but really..... it is just the survival instinct all things natural have.
The environmental stress could be a freeze occurring when the plant was just coming out of dormancy or even a severe drought the summer before when they used all their energy to survive. It could be overcrowding so that there is not enough nutrition to go around or that they are planted by another plant that is using most of the available food.
Producing short, or no, stalks occurs in my garden to newly planted ones or some of the newer more ruffled varieties. The older ones, hybridized 40 years or more ago, do not tend to do this.
Whatever the reason it should not be a characteristic of any iris and will not likely repeat itself the following year. However, with the weather we have had for many months anything may be possible.