Rescue Remedy may do the trick for your cats. You can get it at most JIMBOs stores in the San Diego area, or at a health food store. I think GNC even carries it now. Put a drop in a separate bowl of water and they get a little each time they drink. Don’t put it in their main water though because, if they don’t like it, they won’t have any clean water to drink. You can also put one drop on your finger and let them lick it off or smear it on their mouth if they won’t lick it voluntarily.
Rescue Remedy is for trauma or stress, which your kitties are under due to the outside cats. My boy Devon stressed out at our old house when a stray cat came around and literally shredded the window screens in our kitchen bay window trying to get into the house. I tried everything I could find to keep the stray away from the house (short of trapping him), but never found anything that actually worked. The Rescue Remedy was a life saver for our kitty. It is made for humans, but safe for animals in very small amounts.
