There is no safe answer based only on which unit uses the balcony. Check the registered strata plan to see whether the area is a strata lot, common property or limited common property. Then review the bylaws and any alteration agreement. In B.C., the party that arranges a repair and the party that ultimately pays for it may differ; limited common property can have special maintenance rules. The membrane, railing and surface finish may also have different responsibilities.
Report leaks or damage to the property manager or council promptly, with photos and dates, and ask who will arrange an assessment before anyone applies a patch. The assessment should identify the failed detail and the scope needed to keep water out. Canyon's guide to balcony waterproofing warning signs can help you record useful evidence for that discussion.