I didn’t post earlier as my view is not different from Jimmy’s, but perhaps the Owners Corporation (O/C) [that includes you by the way] is of the opinion that the source of the leakage has something to do with a fault involving the waterproofing below your balcony door or wall; that’s a common fault.
If that’s the assumption or even the fact, then you would be responsible for rectifying the source/s of the leakage and the O/C would, as Jimmy advised, be responsible for repairing the concrete slab which, as it forms the floor of your Unit (balcony) and the ceiling of the Unit below, is common property.
If that’s the situation, then I’d suggest that you approach your O/C about it obtaining quotation/s to identify and then concurrently rectify both the source/s of the leakage and its consequences involving the concrete slab, and with the offer that you reimburse it for the costs of the former IF it’s found to involve your property (i.e. the wall adjoining the balcony and the doors/windows in it).