I'm not a pickling expert but if you pick something, anything, from the garden and toss it into a jar of pickling juice...you left out one step. There is usually some sort of washing/cleaning and the brine mixture is hot to start with.
When I re-use pickle juice, I pour it into a non-reactive pan, heat it up with some extra vinegar, place the sliced veggies into the pan, then ladle into jars and top with the hot liquid.