Gerber start VS similac please help

My daughter is having problems with her milk and we just went to see a specialist and they recommended similac alimentum which did not work any better than the soy, sensitive, or Advance which she was on previously. Any suggestions. It's very stressful to see you LO have to go through this but I would love to here you guys advice or suggestions and yes I did try BF but I had trouble so I don't have a choice but to use formula