I had a feeling this was the case - the recessive parti gene at work. Yeah, your other pups MAY be carriers of this gene, too. So if you sell them, make sure to let the buyer know this.
I'm not sure what the stats are on the parti gene, but I know from biology class, you have a 1 out of 4 chance of having this happen. Both parents have to have the gene and it is recessive. So they would be like RP breeding RP (R = regular, P = parti). That gives these possible outcomes:
RR (no parti gene at all),
RP (carries the recessive Parti gene),
PR (carries the recessive Parti gene),
PP (Parti colored pup; and obvious carrier of gene hehe)
That pic of the pups with mom is too cute!
