just to toss in a different opinion
The suspects:

1 Coral Beauty
1 Yellow Tang
2 Clarkii Clowns
2 Yellow Tail Blue Damsels
4 Green Chromis
6 Red Leg Hermit Crabs

the only thing id take off the list is the chromis, and even then its only because the 2 i
have are very shy and wouldnt fight for anything in the tank.

coral beauty's are IME not coral or invert safe. yellow tangs will eat shrimp and nip at
some corals, clarkii can be evil when they want to establish teritory terrorizing
fish/inverts regardless of size, same for yellow tail damsels, even little hermit crabs
will take any opertunity presented to them. another possibility would be something that
sneaked a ride into your tank thru your LR maybee a mantis or .....

however.

my best guess remains that they molted and some interaction(fish/chemical/shrimp vs
shrimp/shrimp vs rock/.....) durring the molt caused it, ive seen this happen in a tank
with nothing but cleaners happening almost exactly like you mentioned all the sudden gone,
then reapearing with short antennae

there are some things you can do to make the process easier on them, test your water
qulity it should be good. fix it if its not. also feed meaty foods, keeping a variety of
different foods.

--
Richard Reynolds