Sensitive formulas

When did you know you needed to switch to a sensitive formula?

My husband thinks our daughter has been too fussy and farts too much which is why we're trying a sensitive formula, but I feel like she's almost just as fussy/farty as before. If anything, she's even fussier than before but I think it's a growth spurt.

Her poo does seem to have more shape on the sensitive formula. It seemed more like diarrhea before but my husband insisted her poop has always been like that.