If it were me I would take them all up, keeping them separated, in order to discard any with rot and clean up the rest. I would dig the entire bed up and get rid of the weeds and then replant the irises. Put down a weed preventer like preen and then keep them watered every few days until they take root. That is just me. I find that if i take up an old bed bit by bit i miss weeds and little tree sprouts and that puts me back where i was before i did the work. I know that may take some time but an hour each day will have it ready to replant in no time.
