Digestive problem in babies are a result of immature digestive system but there may be little and serious digestive problems in babies. Since they are not able to speak you need to understand whether it is the case of gas, diarrhea, normal spit up or any serious digestive system disorder. Spitting up reflux is a normal phenomenon in infants after feeding. This is called acid reflux. Some babies may spit a bit more than others but no need to worry because until and unless the spitting is accompanied with pain no need to see a doctor. Due to immature digestive system the child faces difficulty in expelling trapped gases in their system which they consumes while feeding, help your child to release trapped gas by exercising like bi-cycle movement of legs or applying little pressure in tummy.
Viral infection leads to vomiting and diarrhea, best is keep your baby hydrated because he/she is loosing fluid out of his/her body. If the problem persists you can continue to keep your baby on liquid diet. If problem persists see a doctor. Transition from breast milk to formula milk, baby may suffer from constipation marked by hard stools, pain during stool passing, give liquid diet to overcome this.