THank you for the replies.

My 5 year old kitty has had peepee problems since he was a kitten. He had an infection once and we treated it quickly and it subsided, but since then his urinary tract has been healthy, it's his behavior that hasn't changed. I don't know why he loves to curl up on towels/rugs and pee on them, I guess he just feels really relaxed when he does so.

I'm still not sure exactly which kitty is having the problem, so I will try something my vet suggested which is to put (non-toxic) crayon shavings into their poo. A different color for each cat. That way, I can see what color shavings are in the poo and determine which kitty is having the diarrhea problems. My 5 year old kitty absolutely HATES going to the vet and it stresses him out even more, so I will first try this test before I subject him further.

Otherwise, he is acting exaclty the same and eating regularly, and has not lost any weight. He is definitely not one to be dominated - he and his brother have a pretty loving relationship, but the new girl kitty is pretty mean to him. My boyfriend thinks SHE may be the one with the poo problem, because she gets poo stuck to the fur around her booty, and she rarely cleans it so I wind up having to wipe it off with a warm cloth, which she HATES!!

I will continue to monitor all of my kitties for another 2-3 days and if it doesn't improve I will take him and whoever else may be having the issue (as revealed by the crayons) to the vet.