I realized that I collected a bunch of snails from Port A that are not reef safe.

Whelks! They eat other snails and like clams. Figured this out when I had a snail (whelk) attached to another snail killing it.

Argh!

Check here to verify you have not done the same:
This link has listings of "reef safe" snails and snails that are "Not reef safe".
http://www.chucksaddiction.com/Hitchsnails.html