My baby is formula fed. I've been switching bottles lately. Was using philips avent but she was spitting up to much. (Later realized was putting in nipple wrong) but was using dr.browns. just hated cleaning those so decided to buy comotomo. She eats but seems fussy at the end. I dont think she was doing that with the Dr.Browns. and notice she isn't eating any more than 3oz at a time. I switched a few weeks ago. Does the nipple matter? I know comotomo and Tommie tippie is for breastfeeding babies.