That however, usually, though not always, comes with vaginal discharge
which is foul smelling and not clear. Occasionally there is no discharge, and that is from "closed" Pyometra, which is even more serious, and needs immediate attention. However both open and closed Pyometra have other symtoms. The dog will probably start drinking an awful lot of water, may vomit, will be very listless, and probably won't eat. If your girls seem very fit and well, it doesn't really sound like this..