In view of poor weight gain (200gm as against expected 900gm) & (possibly bilious) vomiting/regurgitation, & baby getting lethargic, it is safest that you get your girl infant evaluated at nearest medical college/tertiary Pediatric center at Mangalore.
Next Steps
From the history you given, there are a few danger signs indicating possibly unusual causes for baby's condition, (like reflux, UTI, metabolic, outlet obstruction)....which needs physical examination & limited lab workup
Health Tips
Online help without a full detailed workup often is fallacious!!