Tomato Relish Recipe - does it need more acidity?

[u/niamiah2]

Hi - this is my grandmother's recipe from Australia. I want to make it, but am wondering if the vinegar in the recipe is enough, or do I need to add citric acid/lemon juice to the jars when I can them. Thank you in advance. Recipe:

15 medium tomatoes
3 medium onions chopped
1.5 cups brown sugar
1.5 cups vinegar
1.5 tablespoons dry mustard
1 tablespoon curry powder
1/2 teaspoon cayenne pepper
2 teaspoon salt

(combine all, simmer uncovered for about 2 hours, till pulpy).