Low Breastmilk supply and is supplementing formula

Good day Mommies and Pedias if meron. Been trying alal my best to max out my milk supply pero very inconsistent talaga 😞😞😞 Had to supplement formula para mafeed ang little one ko (3 weeks old) but the problem is meron mga reddish color sa poop niya? Sabi ng pedia nya baka nabibigatan sa nutrients yung tummy niya, it does not happen if she's on breast milk (if marami). Ano experience niyo with formula supplementation mommies and ano suggestions niyo? I tried S26 and Enfamil NuraPro. Both ganun kaya afraid ako to give full formula but also worried kasi baka underfed si baby if she will only have breastmilk kasi sometimes parang wala syang nasusuck masyado based sa mouth reactions niya. Hoping you can share to me insights po Mommies. Maraming salamat po ❤️❤️