If he's laying on the bottom listlessly it may be the dwarf gourami disease (I can't remember the actual name of it) that effects a good chunk of them. To me it doesn't look like any tail is lost, but your fish is folding it's tail inward. If it is the DG disease there's no real known cure.
Is it possible that the Bolivians are teaming up on your DG? All three fish are territorial. Bolivians aren't really fin nippers, but they can push other fish around when they want.
How big is your tank?