We had my daughter on the Costco brand formula, Kirkland, which is the generic of Similac advanced. She started on Similac then we switched her to the generic shortly after and she was fine for a while. Then i started noticing symptoms of silent reflux, so I called the ped who prescribed her Ranitidine (generic for zantac). That didn't help, so they tested her stool for a milk allergy and it was negative. She still wasn't getting better however so I called them back and they suggested switching her formula to Nutramigen. She has been on that since Friday, but all weekend she has been spitting up a lot, with the silent reflux she never spit up so this is unusual for her. She has also had several diarrheas a day, and several loose poops. We know when she poops because she screams I assume because it hurts her bottom. I worked in a daycare for six years with infants, so I am positive that it is diarrhea. I am going to call the pediatrician when they open, but I'm getting frustrated because my daughter is in pain and there suggestions are working. Does anybody have any suggestions for similar experiences?