Crocea not looking too happy

[UrbanSage]

Hi,

This crocea has been with me for I think about two years give or take a bit.
It has been visually doing great until recently (last three weeks at the most) after which it has taken a turn very much for the worse.
I have seven other clams counting derasa, hippopus and maximas all visually appearing to be in good condition.
Water parameters are all good meaning ammonia and nitrite assumed to be 0. Haven't tested in years other than cheap giftfromfostersmith test strips. Nitrates and phosphates appearing as 0. I admit I do not pay much attention to these parameters.
Calcium has been running in low 500's and are being brought down via water changes while CA reactor is off, and baking soda is dosed to keep alk at around 9dKH where it tests consistently. Temp sits between 79 and 81.

Lighting is 3x400w 12,000K ReefLux MH. Total flow is an estimated 35x

Here is the poor clam. Any ideas?

And since the ID posting guidelines recommend a tank shot, here it is:

 

[UrbanSage]

Actually.... looking at the porites? in the front of the clam being stung pretty badly by the galaxea. Can this be the cause? Everything has been there for over a year now with the porites having taken a beating for quite some time beyond the period the clam has show deterioration.

 

[neal&bob]

I do think you having some chemical warfare and stinging going on may be a cause. Plus the clam doesn't look like it is getting much light.

 

[johnnybravo234]

The galaxea could do it. Chem warfare will not bother the clam. List all of your inverts and fish.