Katy, i have always been told to not feed any doggy treats to pups, only cheese or something like that for training purposes, treats are often very fatty and give the pup too much energy which could contribute to bone problems OCD, HD, this is why you are finding him a little overweight, the treats are doing no good!
not trying to alarm you, but personally i would cut the treats right down, or better still dont feed them, just use ham, cheese when training as a reward!

Just my opinion

Edited tohe looks very healthy and happy though, hes a great boy!

Luna's treats were her food. I never gave her anything else.

Well when we started training, I started using sausages, but I think Luna was 6 or 7 months old

yea, thats fine jeanette, sausage is fine for training purposes, ive just been told so many times about dog treats, biscuits, they just arent worth the trouble they can cause