Did they have their 12 week vaccines recently? As that can upset their tummy.
My little one was doing the exact same from about 7-9 weeks. No idea what was causing it but it’s now stopped 🤞 she’s now 11 weeks. I have massively cut down on my dairy intake but not sure if it’s linked x
Same happening with mine at the moment! Apparently it could be she is not getting enough fattier hindmilk. I've been advised to refocus on latch and making sure she is draining the breast well. Hopefully it will help!
Look up lactose overload - usually linked to oversupply x