Elderly tenant 'missing the mark'?

[Remmy Vernon]

I have two inherited, elderly tenants who complained that their toilet was leaking around the bottom of it. I went to investigate and found that the area around the base of toilet, in the front, was very dirty with what appeared to be old urine. It smelled like it too. In good faith, I cleaned everything up, and replaced the wax seal. 

Fast forward a month later. They are again claiming the toilet is leaking around the bottom. My inspection shows the same conditions. The wax seal seems good. The bowl doesn't move around. They truly believe something is wrong with the toilet. They think the discolored accumulation around the base is rust water. 

Again, I cleaned everything up, flushed the toilet serval times, no water leaking from it.

How do I tell them what I think is happening: That likely, the older man ( with dementia ) is likely missing the mark, and getting his pee down the front of the bowl onto the floor?

I don't want to upset them, but I can't keep going over there every month to clean up.

[Chris Simmons]

Put one of those old fashioned toilet cleaner discs in the tank.  The type that turns the water blue.  When you go back and there is no sign of blue water stains on the floor....you know.