Just my two cents, but in a tank that is smaller like that, no doubt when one acro goes it can trigger the others. The living inverts indicate its not heavy metals or the silicone as you've already ticked off on your list.
How was the temperature swing during the move? Did everything get a long acclimation? My experience shows that acros don't like big swings in temp (lost half a tank that way). Also clams don't like acro deaths in a big tank or the other way around as well (I've experienced both of those too).
If I were you I'd get those clams out of there to someone elses tank, preferably a tank with nothing else in it (I hear Tony has an empty tank
). Its better than nothing. Then run carbon in a canister filter/phosban reactor or something and change it out every 3-4 days or so and do lots of water changes.
Hope you get this licked, its bad enough having to move a tank but to have major losses as well, that just sucks
