Bulldogs World

I have not fed Buford chicken based food since he was under 6 months old- he is now 3.  I had him on Nature's Variety Prairie Salmon but decided to try their raw patties - chicken as a morning meal and then the Salmon kibble at night.  So far so good.  I then decided to switch from the Prairie Salmon to the Instinct Chicken (grain free) at night while keeping the raw chicken patties in the am.  Well it has been 6 weeks on Instinct and he has developed a nasty raw nose rope and he acts like he is itchy all over.  So my guess is it must be the chicken?  I am now switching him back to the salmon.  Has anyone had any problems like this with chicken?  I was just experimenting on how to improve his coat, reduce his out of control shedding and improve his wrinkle discoloration.  He has never had his nose rope look this bad and this itching all over behavior.