2.5 month old milk intake

My 2.5 month old seems to have dropped her milk intake significantly this week. The previous week she was able to take about 600ml a day but this week her intake dropped to 500ml a day. Worried as her recommended intake for her weight is about at least 700ml a day. Her weight gain/headcircumference gain has been on the slow side😔 Any one also experienced this or know whats happening? #pleasehelp #1stimemom #advicepls