Irises normally need to be divided every few years, so if yours have been in place for 5 years, it is likely that they would benefit from being divided later this summer. The bulblike growth you describe is not likely related to that condition, however. Did the flowers bloom normally this spring? Are these possibly seed pods that formed where the flowers were? If so, you can simply cut off the stalks with the seedpods. It's a good idea to remove the spent flower stalks anyway.