Help! What is happening to my Nems?

[AlohaJacklyn]

Ive had 2 nems die this way in the last 3 weeks. It looks like its being eaten from the inside out. All other corals are perfectly fine and even splitting but these variety of nems seem to shriveling recently after having them for a year. What could be the issue?

*Ive added a video of my other nem variety to show they look healthy and huge in comparison.

*I have 9 nems (same variety).
*I live in Hawaii and have access to saltwater from miles out so i do at least 30-50% water changes.
*Parameters all within safe ranges.

 

[Nano_Man]

Have you changed anything since this started happening
Also do you run carbon in your sump or filters
Have you changed any lighting
Carbon is good for removing toxins / chemical war

 

[Dburr1014]

Parameters? Safe range is different for everyone. Please list.