Baby not eating a lot?

lvisser

Ezra has been on formula for about a week.  Since hen he's been drinking 4 bottles a day equaling about 16 oz a day (Wednesday was 12).  He's a happy baby, sttn 11 hrs and taking two good naps.  He seems to be gaining fine, just slowly... Is this cause for concern?  Today he's had only 4 oz, but isn't showing signs of wanting more....