Hi Suzann:
Angel wing (“reversed wing”, “backwards wing”, “slipped wing”) as you describe can be a genetic and/or nutritional caused condition. If it is caused by diet, it means that there is too much protein in the diet. You need to feed the swans a mixture (50%-50%) cracked corn and poultry layer pellets. Add lettuce and Alfalfa which has in some instances, reversed the condition. You can use alfalfa pellets, however, at this late of an age, the condition may not correct itself. This means that the bird will not be able to fly. The Regal Swan