Are you trying to float the Bismuthinite before or after the other sulphides? I've seen references to Bismuthinite having before floatability at pH<9 but obviously can't use those conditions with significant amounts of pyrrohite, pyrite & copper minerals.

Sodium sulfide or similar reagents (BK510 - Chinese reagent) have been used to depress Bismuthinite while other sulphides are floated.
I will suggest using NaSH to get the Eh to -300mV to depress all other sulphides if you want to float Bismuthinite before anything else.

Can you provide some more details on the liberation and sizing of the various minerals - bismuthinite and all other?

What is your starting bismuthinite grade in the bulk concentrate?

Of the two iron sulphides, which one is the predominant - pyrrotite or pyrite?

What kind of copper minerals do you have?

Finally, how aggressive was the bulk flotation - was it with an excess of potassium amyl xanthate? If so, it could be though to regain selectivity after it.

Lime and sodium cyanide is one of the few combinations capable of dealing with both pyrrhotite and pyrite in one flotation stage. However, the required sodium cyanide consumption could be high if the copper minerals are secondary’s like chalcocite which is attacked by the cyanide.