
I'm sure more knowledgeable people will be along shortly but in the meantime- when you say you are feeding royal canin, csj etc, are you feeding just dry kibble or do you top with tinned? My dogs would rather starve than eat dry kibble. Some are quite happy if you add some hot water, let the kibble soak and cool to release the aromas before putting it down. Mine prefer a little tinned meat mixed in. I started off with the gravy variety to coat everything but now they all have it with tripe.
Not sure if its right but have always been told never to feed kibble mixed with raw as they ferment in the gut at different rates and are digested differently. If you do want to feed a 50/50 diet, do the raw in the morning and kibble overnight. I feed mainly raw and only kibble incase I need to go away, so its easier for the person looking after them.
How are you feeding? Do you take it away if uneaten or give free access? Try putting food down for 10/15 minutes then take it away and trying again later. But whatever you do, choose a food and stick to it. My recently passed friend had a dog a long time ago who kept refusing food. She started cooking roasts and making gravies which he would happily munch. This went on until she was roasting 3/4 times a week and he continued to refuse kibble because he KNEW she'd give in and give him what he wanted. The vet told her to stop. He'd eatnwhen he was hungry and not starve to death. Dogs are cleverer than we think.
If it goes on for more than a few weeks, perhaps a check up?