How do I make my soup go further?

I made a veggie soup last night (carrot, parsnip and ginger with an additional marrow that was taking up half the fridge) and have leftovers today, hooray.

There are enough leftovers for two at a push and I want to stretch it to feed three.

Should I boil up some extra veg/potatoes/lentils and throw them in, or make a second soup altogether and mix them together, or water down this soup?