Answer: Based on your description I am not certain what is happening to your nandinas. Most often fertilizer is not the solution to this type of symptom and can even make it worse.
It is possible that they are losing roots during the transplanting process and this causes them to suffer some drought stress while the roots regrow. Although nandinas can be grown in sun or shade, the foliage would need time to adapt to the sunnier location. So if the wilting and decline is immediate, it may be related to the shock of being moved. The best time to transplant would be in the fall, then allow them until spring to recover and then put on new growth again.
There may also be a problem with the soil. Nandinas require a well drained soil and are very drought tolerant once established. If the irrigation system is keeping the soil wet rather than slightly moist, you may be overwatering them. This can cause root problems which then show up as foliage problems or dieback. Or, if you have fertilized heavily at transplanting you may have overfertilized with the same result of root damage. Or, if you have dug them with too small a root system or replanted them deeper or much shallower than they grew before, these scenarios also could cause dieback. Finally there is a possibility that the soil there is not a good match for this shrub, if it is substantially different from where they were growing before. Sometimes when a house is built the soil along the foundation is disturbed and may not be consistent from place to place.
I hope this helps you troubleshoot, but I would also suggest you check with your county extension and/or local professional nursery staff. They may appreciate photos of the overall plants and their location to help them determine what is happening. Nandinas are very sturdy plants, even with this setback I hope they can be saved.
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