A couple things to try:

-Water source.  Try fresh water vs. mine water.  If the water source is a tailings reservoir, you may be limited, but sometimes the water from the mine gives better control of the circuit.

-pH.  Try lower pH (4.0), normal pH (6.5-8.0), and high pH (9.0+).  Milk of Lime is good way to raise pH if available.

-Grind size. Try coarser grind first to make sure flotation product meets con grade desired.  Fine grind typically yields lower recovery, but depending on minerology could give better recovery.

-Oxygen scavenger. Add a chemical to the grind like sodium bisulfite that will help keep metals from oxidizing.  This one could be tricky with the high amount of oxidized ore.

-Smaller bubble size. Typically reducing bubble size helps recover fine particles better and normally doesn't hurt coarse particles too bad.  This can be done with more frother or adjustments to flotation equipment (if possible).  This will cause a huge drop in concentrate grade typically, so it is important to know what is desired.

Those are the basics. What type of flotation equipment are you using?  Some things may be done depending on equipment available.

Characterise the ore:

• How are silver and gold present in the feed for major ore types- free, as mineral(s), liberated, locked, data by size, etc.
• How is gold present in the tailings for major ore types - same questions as above.