They've likely been separated from the others in preparation for the move, perhaps even moved of display permanently until the move. This would potentially explain why they haven't been seen in a while.
That sounds likely. Dispersal age in this species is 18-24 months, so given the triplets turn six years old in January, Taronga did well to keep them with Kartika for as long as they did.
Taronga has three on display tiger exhibit and two off display exhibits; with Kembali, Clarence, Kartika and Tengah to also accomodate.
With Dubbo’s tigers ageing, it wouldn’t surprise me to see one or more of Taronga’s three older tigers retire there as they look to import a male to breed with Tengah (my money being on Ramah after another 2-3 cubs with Zayana). Taronga are very proud of their Sumatran tiger dynasty, which of course descends directly from Nico and Meta.