R.G.
E.,
It could just be a virus, or it could be the iron in the formula, or something else altogether. First, I highly recommend buying a good Kefir from the store. Helios (sp?) is a great brand if you can find it. It sounds like she might be needing a re population of the good bacteria in her intestines. Ideally, you'll want her on something that contains Bifidobacterium infantis, such as
<http://www.udoerasmus.com/products/probiotics_infants.htm>
If considering a change in formula, and you're not on WIC, try looking into one of the formulas offered by <http://babysonly.com/index.php>.
Best of luck!
Blessings,
Rolinda
Wife, Mother, Friend