The easiest way to tell this from Veronica subtilis is by the shape of a fairly mature seedcase. If you can get them, seedcase shape as well as leaf length and other leaf details, and details of the stem hairs, are helpful in IDing any of these little Veronicas.
Picture of the seed of this plant is available at http://canberra.naturemapr.org/Community/Sightings/Details/3388713 and both Victoria flora key and plantnet lead to V. gracilis
Hi Maartje When you add a new photo to the system, it picks up the information from the new photo, so you will have trouble. It would be easier to just identify them as a pair. Since the dates of the photos are just over two years apart it would be useful to leave the sightings separate. Then you will have the timeline showing that the population is present over that period.