What is this? - Nut grass or Rye grass (Not Onion)

I’ve got this weed popping up in my Sir Walter Buffalo lawn here in NSW. It started showing up at the start of autumn and now it’s spreading pretty quickly. I thought it might be onion grass at first, but there’s no onion or garlic smell when I crush it. I'm starting to think it could be nutgrass, but I’ve also seen some pics of ryegrass that look kinda similar. I’m planning to treat it with Indigo Prosedge 750 DF - just want to make sure I’m dealing with the right weed before I go ahead. Thanks Folks!