Denali is allmost 5 months old, he is curently on IAM"S large breed puppy food and after reading reviews on IAMS we have decided to do the switch over to wellness food (gradually) but we have been told that we can switch him now to adult food instead of keeping him on puppy? We asked the pet store cleark and she said no way keep him on puppy till at lease a year old? So my questions are when should we switch to adult and is Wellness is going to be a good product and which one should we use?