Great Dane Weight Issue!!!!!?

Hi I have an 6 1/2 month old Great Dane who is 1/2 European. Right now he weighs 95 pounds and at the withers is 33 inches. For some weird reason his back legs grow faster so his back is 34 1/2 inches. He is a very big boy tall wise. my only issue is his weight yes 95 sounds like alot but if you see him nearly every rib shows and his spine is beggining to protrude. I feed him CHICKEN SOUP FOR THE DOG LOVERS SOUL LRG BREED ADULT. Anyways he just looks so unhealthy weight wise. His coat is shiny as can be so I know he is nutrionally balanced but weight wise no! Is there anything I could feed him to aid in his weight. White rice maybe?????