What would be signs that a formula isn't for your child

DS had a bowel movement yesterday and the first part (I say 1st part because after I changed his diaper he went again) was firmer than normal then his second part was firmer then went watery and I wonder if that means the formula isn't agreeing with him.

Re: What would be signs that a formula isn't for your child

Consistency of the BMs can vary sometimes -- I wouldn't worry about that too much.

Does he seem like he's in distress at all?
Spitting up more then what is "normal?"
Having a hard time making BMs?|
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With us my daughter would cry really badly when she had a BM and that's how we knew to change.