Baby not drinking milk

Hi mummies. My baby is 7 months. At this age he’s suppose to weight 8.5kg according to the doc in poly. But he’s only 7kg. He drinks milk 120ml but sometimes he doesnt finish it. Only at night when he’s sleeping we’ll give him 150ml and will finished up. Also his eating usually i’ll give rice, carrot and meat sometimes all these i’ll blend but he only eats a little. I dont really everyday gave the same thing. I’ll change recipe at times. How to resolve this issue? Quite worrying.