I have a similar problem. Water from a dishwasher in the unit above leaked through cracks in the slab above and damaged my suspended ceiling. The leak was in the base of the dishwasher and was about a litre spill. Had there been no cracks in the concrete slab the water would have pooled on the kitchen floor, and the leak identified.
I believe that the Owners Corporation is responsible in this case because of the cracks in the slab. The Owners Corporation, now it is aware of the problem, should properly repair the cracks.