Well FWIW dogs were not designed to process cereals, period. This is not a matter of opinion but a fact borne out by their digestive system therefore I see little point in feeding them at all let alone a mixture of them however "holistic" it proffers to be (ask them how they intepret the word; appears to be an oxymoron in this case)!
If indeed she is intolerant of one of the ingredients it makes little sense to me to keep feeding it to the dog!
The system may not "desensitise" to it and in fact may become hypersensitive to it and develop into a full blown allergy! This will have the knock on effect of causing gastro intestinal upset, unbalance the gut flora, interfere with nutrient absorption and may also affect the skin and various other organs in a "holistic" way!
I do not know what breed of dog you have however dogs, like humans come into season at varying times due to a number of factors, bodyweight, inheritance, breed type etc etc etc.
As the feed is designed to be "complete" I fail to understand why you are mixing it with another "complete" diet?
Tartar can be easily treated by using fragaria, descaling them yourself on a weekly basis etc etc etc
I would like to know why so many cereals in one food; what is the reasoning behind it, why not one?
If it were my dog and I was feeding commercial food, I would want to at minimum feed something else with only one cereal, it appears she tolerates ND? and if I still had a problem have her allergy tested.
Would you expose a sun sensitive animal to the sun in order to desensitise it?