I wanted to tell u my girl story maybe it will help u with yours.
I have a Boston she suffered from severe allergies. She was on meds twice a day and dermatologist after many thousands of sollars of tests thwy still did not know what it was the vet put her on rayal canin same as yours. She was a little better but she lost weight because she did not like the food. I started research and research I realized the food was making her sick. Royal canin as main ingredient is corn. She was on this food for 3 years. Not wa hell for her.
After so much research i learned that they should not eat corn, soy, potatoes. wheat,i tried these brands. Primal, acana, signature, pure vita. Nulo (freeze lamb liver)
I also learned that organs are very beneficial and have tons of vitamins and minerals they need.
This is what i do, I buy
Any kibble or freeze dried food from the brands I mentioned. i buy fresh liver and chicken hearts, i steam cook them along with pumpkin and carrots. I do half kibble and half of this food i keep the liquid from steaming and mix it and (according to your dogs size) i make the batch for the day and do half morning half at night.
I make a good size batch enough for two weeks and freeze it. (I have enough for three days and thaw as i go)
It took a couple of months for her better but within a few days her overall behavior and demeanor changed. I dont do any meds anymore and she is good. If i do a treat is freeze dried lamb, sprats.
I go to the latino market dor the liver and hearts kidneys. Cheaper and fresh.
This has changed her life. And we have ot been to the dr in two years.