Hi Patrick & Sandra
Do you have drainage pipes that discharge inside or outside your terrace? The planters should have been filled with gravel around the outlet to the dischage pipes, which might have become blocked with sediment.
If they drain inside your terrace, try forcing something like a very long screwdriver up the pipe to see if you can clear any blockage. You can buy a long screwdriver cheaply from the Chinese Bazar in Sabi.
If they drain outside your terrace you really have a problem!
Michelle & Alex