Unknown snail ID. Drupella?

[DemoAllBac]

Hello all, I upgraded my tank some 10 months ago and went with new, live, rock. I went with a combo of Marco Rocks Mauricultured and Tampa Bay Saltwater live rock (So all from the Florida keys), and I've been struggling (failing) with almost any form of SPS since. I spotted these three snails hanging out together near my SPS graveyard tonight and I know I've never purposely added them myself. Some searching makes me believe they may be some variety of Drupella snail, mainly the shape and spines / bumps on the shells, but I haven't been able to find a species with this brownish / black coloration, and it doesn't look like they pop up in the hobby often enough for them to be on the various hitchhiker lists.

Any help appreciated!

 

[Gumbies R Us]

@ISpeakForTheSeas

 

[StartingATank]

Looks like ceriths…….?

 

[DemoAllBac]

Ah, it sure does look like a Florida Cerith (Cerithium atratum), looking at reef cleaners. I've only ever purchased the Dwarf Cerith, so didn't recognize them at all. Welp, I guess I'll look into if flatworms are my SPS culprit instead then.
Thank you!