Canidae grain-free - opinions?

As a commercial dog food this brand is very popular. My dog has MCT, mast cell tumor, and I make his dog food myself with chicken and rice. I add carrots sometimes and green beans other times. That is it. He gets fish oil caps and an antihistimine, benadryl, to keep the histimine in his body at low levels. I am confident that he is not getting anything that would aggravate his condition.