Is she otherwise well and happy? Not excessively crying and fussing badly? Not unwell? Not running a temperature?
Dark green and explosive poos could be due to the lactose in the milk. Try changing milk powder and see if she's better. If not, bring her to see a GP to check if she's lactose intolerant or simply unwell.
My own kid was lactose intolerant (I didn't know at that time) and had green, explosive poop for a few days when I upped her breastfeeds at around 3-4months. It was when I switched to formula that I realised she was lactose intolerant, hence I had to use lactose-free formula till now (21months).