
I had just one who after having two successful matings, returned to a coloured discharge. I was worried of course, but she was well in herself despite being the only one of mine who ever did this, mated or not. She went on to have an uneventful pregnancy and 9 super puppies, from which we kept 3 who came back to the UK with us, and others.
Yes I'd wondered about a Pyo so it may be a good idea to keep a close eye on her over the next few days, and if at all concerned, involve your vet. Fingers X'd all will be well.