I know for sure Beneful has corn/wheat… and is not a very good food. You should go back to what the breeder was feeding, but even that brand has corn but it is further down on the list of ingredients then Beneful. Here is the beginning of the ingredient list for one of the Beneful products: Ground yellow corn, chicken by-product meal, corn gluten meal, whole wheat flour, AND they claim that the use real chicken... NOT by-product meal is not real chicken. In fact every one of their dry foods start with the above items. Corn is a filler, it is of no use other than to fill them up for a dog. Also, it (IMO) raises their body temperature. Consider that farms have fed corn for years in the winter for cattle and for horses to generate body heat. We used to do that for our horses, dry corn on the cob in the winter, but never in the summer months.
I use Evo Chicken and Turkey, grain free and I switch off or mix with Fromms Surf and Turf or Natural Balance Potato and Duck.
And while I would certainly recommend that you feed a better quality food, keep in mind that when with littermates they bite when playing with each other, so could have little scabs from playing that are healing and itchy.