I would say the hard dry root ball was your problem - you rhodies were potted in peat moss most likely and when that dries out, in or out of the ground, it's almost impossible to re-wet it unless you use hot water. Unless you see lots of roots coming out of that root ball I would suggest you dig them all up ASAP, remove all the potting mix (which will be easy to do as it's dry) and replant. Don't fertilize until they show signs of improving (it's like feeding a sick person with a 5 star meal
they won't eat)
