Question about changing formula?

my daughter has had some issues with gaining weight so when i went to wic to get her on formula they gave me half of powder and half of liquid to try both out and see what she eats better. she is eating the liquid better but that isnt enought to last a whole month so i would have to end up using powder at the end of the month...is that bad to do? the formula is the same kind and everything just one is liquid and the other is powder