Dead nudibranch?

[bseahorse]

How can you tell if a nudibranch is dead? Specifically a Doriprismatica Atromarginata. It has not moved recently but is not floating, doesn't smell and has not lost it's coloring yet.

 

[Reefing Madness]

 

[Squishie89]

I'd poke it and see if it does anything