Clam loss

[DocMark]

Thought I would seek opinions.
I have a well established 214gal mixed sps/lps.
Parameters all good (recent results from awt.com) pH 8.1
temp 78.

I bought two clams a 3.5" crocea and a 6.5" squamosa and went in the tank a week ago.
They were acclimated appropriately and placed at bottom of the tank. 26" deep. Tank has two 400w 14K ushios and actinics.

I was going to move the crocea up, but didnt get the chance, overnight has died. Squamosa still doing well. I also have a small derasa that has been in there a couple of months and is doing well.

Only thing I noticed yesterday that it was spontaneously opening and closing repeatedly without stimulus.

Here is pic from 3 days ago:

Any thoughts??
Mark

 

[DocMark]

oh, and there is no issues from predation by fish.
There are a couple of cleaner shrimp in the tank, but never saw them near the clam day or night.

 

[quicksilverq]

What is DK/ ALK
Mag
Calcium
list everything
u cant just say parameters are good.

 

[ezcompany]

kind of looks like pinched mantle in the bottom left of the clam.
also, cleaner shrimps have been known to harass clams to its death. you may want to try and cover the clam with a strawberry basket to see if the problem continues.