So sorry to hear about Presley..it sounds like maybe an allergy to the food?
My sister-in-law's malamute has seizres and they dn't know why. He is on meds ( and the name is escaping me at the moment)but that helps in so much. unfortunatly, it is damaging his liver.
Hopefully just keeping Presley away from the food will be enough for her...poor baby! We'll be praying for you!