hi
i'm not as experienced as anyone else that has been replying - but reading through this it really reminded me of something that happened to another one of dad's tanks back in 2001
he was quite unlucky really, as the year after that was the year of the horrible coumnaris episode!
anyway long story short - we found a lovely bit of freshwater driftwood in a local stream. boiled it, and soaked it. after adding to tank pH and everything was stable, no colour change - but all but two fish died. just went sluggish adn showed signs of wanting oxygen.
he put carbon in filter and took out wood and the remaining 2 fish (a cherry barb and a tetra - cant remember what kind) lived he thought it was pollution from the stream that had soaked into the driftwood. we lived downstream of a really industrial area though so it probably could have been predicted. The main thing that reminds me is that it killed all the moss in the tank too whatever it was.
was your driftwood salvage or purchased? im probably wrong and this is just anecdotal - but something to think of i guess.
really sorry about the outcome for your barbs it sounds like this tank's had a lot of heart and soul (and cash!)