Had pcnl a month ago for staghorn kidney stone, all stones removed now passing small red "stones" unlike any i've passed before, are they stones?

Possibly. : After a major kidney procedure such as a pcnl for such a large stone. Stone fragments, sediment, and blood clots may pass for weeks. This should clear with time, but if you are concerned you could strain your urine (urinary stone strainers exist), and collect some of the debris. This can be examined by the physician in a followup visit.