MIA : 1 x thorny grey starfish.... come out come out wherever you are!
DIA : 1x Coral Beauty...wtf jammed between the back wall and a rock....
now do I pull the tank apart to find these two???
:(
A common cause of death of sea stars is starvation, especially in relatively new tanks - there just is not enough for them to eat. It can often take months but eventually they die. Hopefully yours will reappear.
The coral beauty has probably ended up behind the rocks after it died - a healthy fish will not get trapped between rocks.
If you can get it out then do it - if it means pulling your tank apart then I would leave it and rely on your CUC although you might want to monitor your water conditions and do some extra water changes.
BTW, it looks like you have some bubble algae on some of your rocks - it might be worth your time to try and get it under control ;)