You need to separate them immediately. When you think a snake might be sick the first thing to do is separate them. Nothing in that glob looks like poo or urates... It looks like infection. Could be some sort of parasite issue? If this has been going on for weeks, my advice is take him to a vet. He probably needs antibiotics.

Just wondering... I have no idea what a mating injury looks like, but could that have something to do with this? I know the males' parts sometimes get damaged during mating.