I wonder if it may be the B vitamins? When my first was tiny and took the Poly vitamins she was fussy. When she was taken off and put on the A, D, E Tri version(with iron, it was better. But it was even better on the M O M vitamins in my milk when I stopped the vitamins. Some babies reported to get fussy when moms take Brewer's yeast(remedy for milk supply) and there's lots of b's in that. ER-I missed it, was doing our LLL meeting. :-( There's ER websites, but in my "other" file cabinet, will send later!! Georgeanne Mattise, Scranton, PA