Well, if you know which 2 it might be, the first thing I would do is take them both to the vet to be checked for a UTI. If all checks out then I would move to the behavior area.
First off, if all the males are whole then yes, you do have a problem. You wont get rid of the problem until the offender is taken away from the stress. Usually when they go in one place like the bed all the time(because it is yours and you treasure it) they are trying to tell you they are VERY pissed about something. With that many whole males and females, I can see where this may happen. For now, I would try seperating the two, weather it be either of them in a seperate room. Give it a week and while they are seperate just bring stuff in and out that smells of the other. After a week or so, I would give them both some Dr Bachs rescue remedy and try to re introduce them. Seperate them again if they are really bad with each other and try again the next day. Also, I would order some of that Nok out I put in the first post. While you are doing this, I would pour in onto the matress and then go to the closest store and buy a plastic matress cover, this way it will prevent it from soaking in again.