the tretment you have used is for ponds right? did you get the dose right for your tank?
It could be like ROB-C said the new fish could have brought a infection in with them!
its hard to find out what realy caused the problem and your right to remove dead dieing fish asap so they dont polute and cause amonia/nitrite problems!
i would not think the bogwood would cause this so u can rule that out.

what were your water tests for the aquarium?

good luck i hope they pull through!

keep posting on their progress as threads like this help others !

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