is all profile including liver and serum protein level are normal then edema is commonly seen in preterm baby as extracellular water content is more as compare to term baby and it will get resolve with nutrition build up and weight gain.
2nd issue is hemoglobin
level, u didn,t mention abt peripheral smear of blood and retic count, if it is normal then anemia
of prematurity is most likely cause,don,t panic , if baby,s vital are stable you should give only iron suppliment, vit E until 40 week of conceptional age, and your baby is sure candidate of erythropoietin
therapy if your centre have facility but u can manage without this drug.
3rd issue which is most important is bilious vomiting
i am sure it was not through orogastric tube distaly plasced in dudenum can have this this problem other wise kindly get contrast study to rule out surgical cause. as sepsis
screen is negative gastric hypomatality is seen in preterm baby but in this condition bilious vomiting present only for 2-3 times not associated with abdominal distension.
i hope i am helpful to you than you.