If they are indeed bearded iris there is a distinct problem with pots. Beardeds come in dwarf (you are probably not cold enuf in the winter for these) , medians (IBs, BBs and MTBs) and tall (TB) sizes.

Pot culture is more successful with the dwarfs or medians. The TBs 'travel' (as do all the beards) and quickly outgrow 1-3 gallon containers --- a 1/2 oak barrel is better.

When you see an bearded iris blooming in a pot, it probably has only been in that pot ~10 months. If I were attempting to have these on a balcony, I would look for a container at least 12 inches deep and 15 inches wide. I would use bonemeal as well as a time release fertilizer.

It's not impossible to have beardeds in containers if you are willing to provide their needs. Division depends upon the vigor of the cultivar. A tall bearded is a large container may benefit from new soil & division every 3 years. The small the container, the more frequent. They still need to have the top few inches of soil dry before the next soaking. Beardeds do not have a dormant period in milder winter zones. In summer the outer leaves do age and the clump looks 'tired'. But growth is happening.

The season for bearded bloom is practically over. You can divide yours now.

Thanks iris_gal! From another google search I'd guess that I have the medians. I will try to divide mine this weekend and re-pot them as you suggest.