Following any illness facial appearance get changed for few days. This becomes normal once babies started to take normal diet and recovered fully from the disease condition. In any acute illness there may be loss of hair called Telogen effluvium
and recovery from this condition is spontaneous, may take few months.
By seeing the pic posted on FB you can't properly evaluate the baby. So ask their parents and if they are noticing gross paleness or any other obvious changes, then they must consult a doctor for proper clinical evaluation and management accordingly.