Sorry to hear about Roxie MJ. If you want a really good quality shampoo, I use Yorkie Splash. It's made specifically for Yorkshire Terriers by a Yorkie breeder who makes it by hand, it is made from all natural ingredients and has a great PH balance. It's not expensive. I use it on Sophie and it makes her hair feel and smell great. PM me if you want more info. As far as Royal Canin...I feed Sophie Eukanuba small breed puppy kibble. Eukanuba also carries a Yorkshire Terrier breed specific adult food that's made for their particular coat. Sophie has had no problems with the shampoo or food we use. Good luck and I hope Roxie feels better soon.
Jackie & my 
Sophie 