My ferrets rib cage and body structure

My ferret is an old ferret and he eats very well and drinks normally. Although he seems to be fine his rib cage sticks way out of his body and he is very bony. This slowly started to happen and it looks unhealthy. He does eat very well and i am feeding him Nutrient Rich Ultra Blend. he is not skinny looking and his belly is nice and round but he ribs stick way out and im afraid that its going to get worse. Bandit is reaching the ferrets normal life span but i want to help him because even though he is old he is still active and likes playing but because of his problem with his ribs and bones it has slowed him down a bit. I live very far away from a vet so if you could plz help me and tell me how to help him I would like to save myself the long trip but I will bring him if needed so that he can feel better.

Most of us on here feed soupies daily. All 4 of mine get it 3x a day. I usually soak kibble overnight. The next day I put it in a food processor and blend with water, egg, pure pumpkin and heavy whipping cream. The pure pumpkin helps with hair balls and the heavy whipping cream helps put on weight. Part of it is probably because he's older now. 

 
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