Too many "treats"

Hi

I have a chihuahua/min pin mix who is three years old. We just got her yesterday actually, and the previous lady who had her said to give it a treat everytime he goes to the bathroom. however, we take him to go out multiple times a day (since we live in an apartment) and i wonder if that is curbing his appetite for a meal becuase he never seems that interested in the food i put down for him.

I dunno if its because his full on treats, or if he misses his old home, or if he just doesnt like his food.

Any suggestions? itd be greatly appreciated.

Thanks.

Nicole