I suspect it’s not like others have suggested. That the drain pipe drains only the balcony floors and will be useless to catch any water when cleaning the exterior glass of a glassed-in balcony?
And worse, all the balconies, even the originals, now probably splash water down onto the exterior glass of the glassed-in balconies?
Professional exterior window and balustrade cleaning for the whole building?
It will be expensive but they will start from the top and work their way down. For some buildings there’s no other option.