Is this PMD?

[MoparMike97]

I’m assuming you had them all for a while. That’s so unfortunate. Did you try dipping any?

At the time I started losing clams, the newest addition had been in the tank over 2 weeks. I tried doing 30 minute FW dips 5 of them, but as it had no effect whatsoever, I didn't bother with the rest.

Like yours, basically all of my clams were showing great growth and looked perfect, then began showing slight retraction for a few days before quickly deteriorating and dying. Some people said it was possibly a protozoan called Perkinsus or an unknown virus.

Really sorry to hear your other clams are starting to go downhill.