I believe that C&G and Aptimal are the same! I would check with your HV, but in our case, LO hated SMA (Aptimal from birth, wasn't feeding in NICU, they tried him on SMA, seemed to work for a day, back to Aptimal, but it was a too small teat that was the problem) -- perhaps try the next size to confirm it is the formula and go from there!
best wishes