8 week old eating way less

When should I be concerned?

My LO was on AR formula where she was drinking 3oz SOMETIMES 4 (in the night).

We had to switch her because she had horrible constipation, we switched to similar Alimentum and I noticed she’s drinking way less but also, about a week now she’s been sleeping way longer. But I’d think she’d drink more when she wakes up? No, she can go 3hrs and maybe drinking 2oz and maybe an ounce here and there I’ve been tracking and so far it’s 7pm and she’s drank 10oz since 8am. That seems really low for me?

Is this concerning or does it sound right?