Children feeding can be rather variable from day to day and if they are sick also can be quite different.
To answer your question properly though, we need the following information such as the sex, weight, race of the baby as well as the type of milk. Also relevant medical history.
A sudden drop in feeding can be due to many factors and sometimes they can be sick and need to see a GP/PD. Whereas sometimes could be simple things like change in the caregiver or the nipple.
Assuming the child is average in singapore, assuming a weight of about 5.5kg, they will require 120-150ml/kg of formula milk daily. The feeding works out to be quite within the range.
Also babies sometimes can have short periods of growth spurts when they drink a lot and some periods when they drink lesser.
If you are still facing problems, we should have a look at the child to figure out.