Hello everyone! My son is 4 months old, we're not on formula, only…

Hello everyone! My son is 4 months old, we're not on formula, only mixture, about a month ago he even doesn't want mixture, or I don't even know, his normal is 150-180, and he drinks only 30-60 during the day, at night 90-120, I can't understand why, he doesn't cry, everything seems normal, I'm afraid we might lose weight ?. By the way, a month ago started giving him Dromamarin vitamins, maybe he's full, I don't know at all... Has anyone had something like this?