Ok, well for starters... From what I gathered from the way you worded it, you have 3 clown fish, and 2 bangai cardinals, and the rest of the fish...
Well you cant have 3 clown fish together because one will become dominant and one will be shure to die or in your case maybe 2.
Bangai cardinals are very agressive towards eachouther as they mature with age unless they are a mated pair.
The missing bodies are very common in a reef tank since your hermits, shrimp, snails, and creepy crawlers usually clean up an entire average size fish over night. The cardinal was draged under that rock by these creatures to retreat from the light so that they could safley dine on it.
Sooooo...... I'm sory to say but your fish probably killed eachouther.