Dupes Passing Sink

Did the dupe have germs on it? They only use sinks when necessary.
 

The way its pipe would probably cause this. waste water from the toilet will block the output pipe on the sink

I didn't check their germs specifically but some of them had to of. This was just after I saw germs had been spreading farther around the base than I would have liked and quite a few dupes coated in germs. I did try changing around the pipes too but even when nothing was going through the output they weren't getting used.