Have a labradoodle puppy aged 4 months. Came to us on doctor johns puppy food however he was not having any solid poops. Tried just the kibble with no other treats but no luck. Sent stool sample to the vets and no issues. Have changed to harringtons turkey and rice puppy food just over a week ago and they seem to be worse, less formed, more light brown and with an odour. How long do we leave him on the new food to get good effect? And any recommendations for puppy food for this kind of thing??