my LO does the exact same and they’re similar age, it’s completely normal just keep an eye on on how much they are weeing and pooing because if it’s runny get it check etc i’m rubbish at explaining but you are totally okay to freak out at first it’s normal i sure did to the point where i was changing and she carried on doing her business and my eyes started watering because it was so strong smelling👍
I noticed my 16 months old poos smell sour when she’s got teeth coming in x