Girls, there's a problem, since birth they eat formula, stool was yellow…

Girls, there's a problem, since birth they eat formula, stool was yellow and good, then started greening and becoming liquid, gave him Simethicone and Bifidobacterium, reaction became yellow and good, then again as if not giving these drugs, green liquid stool, what to do at all I don't know. The doctor said take Bifidobacterium for another 5 days.