Newborn started with formula and now breastmilk, apetite decrease?

Babies appetites change all the time. My daughter is a month old and sometimes I get her to eat 2 oz and other times she wants 5 oz. Usually formula is more filling and takes longer to digest, but if her appetite has changed I wouldn't worry :) As long as she has 6 wet diapers and 2 bowel movements a day at least then she is doing fine.