Usual strong TFR mix has tarnished the rubber. You can try using a bumper trim gel to restore the finish, but it will fade eventually. Personally I would take it back and get new rubbers!
that could well and looks like it needs new rubbers , and most/all products will be masking hiding the problem , Gtechniq C4 would be the best solution and would need recoating around 12-24 months.