You won't be able to use reference lines to do that kind of job. You'll probably have to change your chart to a combo chart like maxgro mentions then create an extra expression for those bars. You'll have to use a symbol instead:
Here is an example chart with dots:
There are other symbols as well, but none that match a vertical bar.
If you are insistent on the vertical bars, you may use a bar instead and then play around with the bar offset and then in the expression, you'd have to figure out how wide you would want it:
But this may add some complexity.
Hope this helps!