if the holes are on the underside of the rhizome then i wouldn't worry about that, alot of mine have them from where old roots fell out. if they're soft cut off the living part and replant the rest because it could be iris borer or a resulting case of soft rot and could spread.

if the rhizomes aren't soft, and especially of those holes are on the bottom then i wouldn't worry.

I had a bed of iris' that I hadn't split in about 5 years. Way past the split time and they looked like yours with the holes, but weren't soft or squishy. When I split the bed I had triple what I thought I had. Gave some away and transplanted the rest. Haven't had a problem with any of them. I agree with ashes of the fire, if they aren't soft I wouldn't worry about it.