It looks like it is sitting on a tray of water. Cordylines like free draining moist soil, not bogs. I think that is part of the problem. Settling in is probably the biggest problem and one that sorts itself out. Is CA a good place for Cordylines? They do fine in the PNW and the UK but I wonder if CA is too dry?

Drooping since yesterday usually means shock, caused by root damage while transplanting. Socal, did a lot of the potting soil fall off when it was removed from the original pot, or did the root ball stay exposed to air for a time? For treatment, I would prune off about a quarter of the oldest leaves--the ones on the bottom--and use a good root stimulator.
Botanic, Cordylines do fine in coastal California, but are much more difficult in the deserts to the east.