A 6-month-old baby, weighing 3.2 kilograms at birth, was initially breastfed for the first two months, then switched to milk feeding and supplemented with calcium and vitamin D. However, after hospital treatment for upper respiratory tract infection on December 22, the baby began to show symptoms of decreased appetite, reduced sleep, night crying, sweating, and weight loss. In addition, since switching to two-stage milk and rice porridge, the baby has started to frequently vomit and experience diarrhea. The baby currently weighs 10 kilograms.