You can cut the foliage back on the smaller canes. It may be best in this situation to just remove the damaged leaves one by one until you get to new growth deeper in the crown. Once watering conditions have been stabilized, new leaves will grow. If the damage is too extensive, cut the whole leaf bundle off; if the cane is still healthy, it will grow a new leaf crown or two. Be advised if the whole leaf bundle is cut back to the stalk it will take some time for the stalk to grow new foliage, so be patient.