Jim,
That is the pint of the scandal - nobody knows who they were and why they died

Then there is no scandal Jim, because the deaths are all registered.

Guardian,
"The institution, which looked after children from broken homes, opened in 1864 and closed in 1981. More than 11,000 children stayed at the orphanage over that period.
Records reveal that most of the deaths were due to natural causes, mainly from diseases such as TB, pneumonia and pleurisy. About a third of the victims were under the age of five, and the majority of the deaths occurred between 1870 and 1930.
Former residents of the orphanage uncovered a burial plot containing the remains of a number of children at nearby St Mary's cemetery in 2003."
"An inquiry by BBC Radio 4's File on 4 and the Sunday Post newspaper examined death certificates in archives and found 402 children from Smyllum Park.
https://www.theguardian.com/uk-news/2017/sep/10/smyllum-park-lanark-orphanage-catholic-nuns-children-mass-grave-allegedly

BBC,
"The death records indicate that most of the children died of natural causes, from diseases common at the time such as TB, pneumonia and pleurisy.
Analysis of the records show that a third of those who died were aged five or under. Very few of those who died, 24 in total, were aged over 15, and most of the deaths occurred between 1870 and 1930.
One of those believed to be buried there is Francis McColl. He died in 1961, aged 13; his death certificate indicates he died from a brain haemorrhage. "
http://www.bbc.co.uk/news/uk-41200949