Yep, I had some on some play sand that turned anaerobic and they lost their barbels. Changed the substrate to stuff I could keep clean and they grew them back good as new in about a month.
Cories actually like sand but the sand shouldn't have sharp edges nor should it be left to become compact wherein if disturbed, it will release hydrogen sulfide killing the fish in the process. Try adding Malaysian trumpet snails to help stir the sand.