Hi mama! Oo, totally normal yan, babies on mixed feeding (formula + breastmilk) usually have poop na slightly different from purely breastfed or purely formula-fed babies, kaya baka you'll notice it's a bit more brown or thicker than expected. A few of us moms noticed the same thing with our babies, and as long as baby's happy, gaining weight, and hindi constipated, you're good! If you're worried about color, consistency, or frequency though, best to check in with your pedia para lang sure, lalo na at 10 weeks pa lang siya.