Feet issues

[RyRy]

We have had our axolotl for about three months. His feet appear to be wearing away. First the claws, then the toes, then the foot. What could cause this? I do wonder if the substrate is not smooth enough? It is Seachem flourite black sand. Any thoughts would be welcome.

 

[Skudo09]

Are you able to post some photos? What are the parameters in your tank? Any further details may assist in determining what might be going on.