Hi D.,
You may be being paranoid, but I think EVERY mother tends to be. Her is my feeding story and I hope it helps. I breastfed my son exclusively for 3 months. Then he went into daycare where it was a mix between me and Nestle. I think I remember those metal pieces and chalked it up to the lid and inside of the container. (If I remember correctly) Anyway, when he turned about 6 months, my husband the "label reader" checked out the ingredients of the Nestle vs. BJ's and found little difference and the differences were not important. Also at 6 months maybe 5 1/2 we went for the rice. So, that is my feeding pattern. Not sure if it helps or not, but what I can for sure tell you is that NOTHING we've just talked about that you do will hurt your daughter. She may get an upset stomach or belly ache or gas...but nothing serious that can't be reversed. If you find a strange symptom, removed one thing you've changed and see if it works. Just trust yourself and you will do great!!!