Dead urchin?

[pseudorand]

I think this is the remains of my tuxedo urchin. Can anyone confirm that's what they look like dead?

I had it for about 2 years. Is old age a likely cause, or do I need to start testing everything under the sun?

Here's his brother, still collecting shells.

 

[Reefer Reboot]

It's just decoration now.

 

[vetteguy53081]

Ive seen my own urchin lose all structure to have it come back. Its likely osmotic shock or stress causing this. Starvation alone can impose stress. Shock would be a change in water or environment.
Check for elevated nitrates or phosphates.