7 clams dead in 3 weeks

I need some immediate help from all you 3reefers to try and figure out what is going on. As the title states I have lost 7clams in the last 3 weeks. I have no idea why. I lfs owner has been trying to help but I am now reaching out to you all for ideas.
My water params are:
pH 8.2
SG 1.026
Salinity 38 ppm
Amonia 0
Phosphate 0
Nitrate 0
Nitrite 0
Calcium 440
Alk 9 dkh
I don't have a Mg kit so I couldn't test that.

I run 6x80w T5's. Bulbs are about 5 months old. The daylight bulbs are on 6 hrs a day and the actinics are on for 8. Am I missing something? I've only 2 clams left.
I do frequent water changes and maintenence. Everything else looks great. Sps, lps, softies all great.
Lights are 20" from the bottom. The white bulbs are on for 6 hours a day lights are on

 

Clams can get Pinched Mantle Disease and that can spread to other clams, try researching that up. i hear Fresh water Dip is the cure. just read the DIY

 

How long have you had the clams/ have you moved them recently or made any changes? Also, are you dosing vodka, I have heard of people losing them and linking it to vodka.

I've never had a clam in my tank before so not much more help then those possibilities sorry.

 

I have had all these clams for months and some for years. They started dying smallest to largest. No vodka dosing. My clams don't drink and neither do I. But I'm about to start.

 

I lost 7 clams the same way. Its was after I introduced the last clam and I supsect a parasite/virus I could not identify

 

That's not what I wanted to hear. But thanks. I thought of that being a possibility.

 

I cannot help directly but I can help with broadening the information you're providing. What kind of flow do you have going on in the tank, and have their been any recent changes? Anything change feeding wise or such? Any new additions of Live rock or corals?

 

Forgive me if I ask the obvious but you have ruled out PMD and Pyramids? You did not mention that in the original post.

New new additions of GFO, phosban... recent change in carbon type or amount?

What size and type are the remaining two?

Have you considered a FW bath for both simultaneously?
Do you run a UV?

 

Lots of flow, no new livestock added for months. I don't add much livestock. I know its not snails I looked fof those on every clam. Not sure about pm. No changes at all in the setup. I have 2 Derasas left. Both nearly 10". And I occasionally run uv.

 

Ok

Do they die over night? Do they take days to succumb?

Have you seen any large worms, looked for Polyclad worms?

Do these remaining clams look healthy?

I would change out the UV bulb if it's old and run it consistently. If they clams are stable I would also do the FW bath, same temp same pH.