How funny is funny? It’s supposed to be pastey but if it’s runny like watery I’d talk to your doctor. Could be diarrhea and the sour smell would concern me too. Their poops don’t generally smell sour unless something is upsetting their tummy.
Ours has gone through the same thing too! She's 8 weeks old and it started a couple of weeks ago. Our HV explained that before now she had basically been incontinent and now she actually has more control over her bowels. Ours now goes once a day/once every other day. Much runnier and smelly! Checked with the GP on her postpartum check and they were happy with all the information we gave xx
My HV explained to me that their habits start to change around now as they become more aware of their digestive systems. My girl is 8 weeks now and before 5/6 weeks would go a massive amount every day, sometimes multiple times. Since then she goes every other day and will have like 2/3 big movements in a day. Then go a few days without again. This seems to be her pattern atm EFB too, and sometimes her poop is looser than others but always mustard yellow and sometimes with a sweet smell.