My son has a 2 year old English Bulldog…..He has been on Royal Canine food since he was off of puppy food.He started to not tolerate it very well,so my son just changed him to Blue Wilderness Chicken ..He is mixing it to his Royal food in small amounts to get him adjusted…after about 5 minutes he is throwing it up…..what do you suggest? He isn’t on a regular feeding schedule because of the way my son works…can this have a impact on him?His stools seem loose which i feel is from changing his food but how long will this continue?Any help with this matter will be greatly appreciated..Thank you in advance Linda