Just mentioning also there is not a newspaper I have located named the Healesville Gazette on Trove.
I do see the Healesville Guardian, but digitisation does not seem to include the year 1883.
Do you have actual sightings of Alexander IRWIN in Victoria?
I cannot see an immigration in 1861 per Lightning as you have suggested for Sarah IRWIN, though there is one in 1863
Her death notice suggests 1861 arrival....??
The lass on Lightning 1863,is English and b. 1838.
Sue