Not specific to Jack Russell but please bear in mind that the muscel controlling urine tract in a pup is not strong and a pup might wee on the way to the toilet spot. For example if you are upstairs it can wee on the way downstairs.
You do know, I'm guessing that all dogs do like to do wee after eating.
You therefore need to encourage the pup to the spot and give a command - do wee wee. Be patient. Once it has gone, lots of praise. Good girl, good girl.
Please tell me that balcony is 100% safe. May need extra protection lest it fall between bars when it gets excited at some sight.
Might sound strange but it's happened heaps.
You obviously have something in mind re litter tray.
Pups can also wee when they become either nervous or excited. They just forget.
Under NO circumstance do you hit a dog because of an accident.
Nor do you rub the dogs nose in it.
Keep reminding yourself in human years how young it is.
Be observant and regularly encourage to the spot with the command -do wee wee.
It is not healthy for a dog to be asked to hold on too long.
Mine are general comments only and it's a breed I've never owned.
They do have an association for the breed and it may be worth giving them a call.
Good luck with mans best friend.
May you get maximum enjoyment from each other.
