I had the same problem with my daughter and her getting different formulas. The poo would have a very clear silver sheen to it. We saved it and brought it to the doctor and he didn't seem to concerned. We tried switching formulas and it did get better once we were on a different one. I can't believe that I can't remember which ones but we tried Similac, Enfamil and Good Start. If she isn't acting sick I wouldn't be too concerned; I was overly cautious, since it was my first baby. Good Luck!