Genetic mutations

I think there is something wrong with Spike.
Silky Terriers are said to weight an average of 3.5 - 4.5 Kg.
Certainly there is always a chance that you end up outside this range.

However, Spike now amasses 6.8KG now with NO flabby fat whatsoever.
I am afraid he will turn out to be a Silky Terrier Doberman mix...