3month old girl presented with not gaining wt . Her birth wt was 2.9 kg now wt is 3 kg. she is on exclusive bread feed. No any significant neonatal history, no h/o vomiting cough, fever , res distress , no cyanosis , no murmur. Hr 144/ m RR 24/ m .

Maternal history is not signicant. Investigation like CBC , tsh , vit d , karyotype, echo report are awaited . What is deferential diagnosis? Please help.