Aww, not that you adore him or anything, look at his little face all squidged up to yours
Bella suddenly became a bit rotund at 6 months. We didn't realise till we got her groomed and she came back looking like a portly Georgian gentleman, a fabulous wig hair-do, little stick legs and a big belly! She was only about 3/4 of a kilo over what she should be but it really showed - she'd lost her waist completely. She was put straight on a diet and about 3 months later was looking nice and slim again.
So now I'm paranoid and always checking her figure. The ribs should not be visible but you should be able to feel them if you run your hands along his sides. They should have a slight waist (I don't think cockers are prone to having hourglass figures
). The other thing I've learned with Bella is that when she's nice and slim, from the side, she kind of nips in at the side of her belly, so where her ribs end and her abdomen starts there's a kind of dent at the side, if that makes sense.
He's a gorgeous boy regardless!