Upper lip of the seven balconies' brickwork may need re waterproofing

The below four pictures from my balcony evidence that remaining cement in between the top row of bricks varies markedly, seemingly because after almost 50 years falling rain water has washed away some of the cement. Most evident in the third below pic where water might be penetrating the wall and slowly destabilising it. 
I don't expect that it would be a difficult or costly task to apply a squeeze out waterproof sealant to the one in four or five cavities on each of the balconies that are similar to the centre cavity in the third below pic.