Naso2
triggerfish
What are your tank specs?
Upon closer inspection of the pics I'm also concerned about your clam. I'm no expert but I do know when the *Inhalent Siphon* is stretched open such as yours is, it is struggling to survive.
Here is an awesome read on the T. Crocea.
A Close-up Look at Tridacna crocea by James Fatherree - Reefkeeping.com
I agree with you.