Clam question

[michika]

Okay I've posted this on Clamsdirect's forums but I need a second or third opinion.

What is happening here:



The clam was fine yesterday, and then this afternoon it looks like this.

Parameters:
Sg 1.025
Ammonia, Nitrate, Nitrite: 0ppm
Ca 420ppm
Mg 1300ppm
dKH 7ppm

Last water change was last Friday. Nothing has been added or changed in the system since then. There was one fish death on Saturday, but it was cleaned up immediately.