
Give the Royal Canin 'Sensible' a try. It has a higher fat content and when my Dalmatian suddenly developed an on going upset tummy on the normal adult they suggested I tried him on that, they even gave me a free bag.
It worked a treat, but what works on one dog, may not work for another. Funnily enough I have tried Pro Plan in the past and I lost coat shine on my Border Collie, where as the RC has always given her a lovely coat.