Coralline die off is normal when cycling. You shouldn't lose that much. It also depends on what lighting you have on the tank or curing set up if any. Once added to a tank with higher more intense light there could also be some bleaching as the coralline adjusts.
If you are curing in the tank and the levels have stabalized, do a large water change with well aged SW
to bring the chem back into balance. Test the levels and be sure all is well. Once the tank parameters and chem are back in sync, the coralline should recover just fine depending on the lights you have. Having good water flow within the tank will also help spread the coralline spores a bit better.