I'd suspect the flashing where the rooflets meet the wall. Scrape at it and take some closeups. I don't know flat roofs well, but it might be concrete, or a wooden deck, with an asphalt, tar or metal covering. The edge should be stepped up to prevent water running or pooling against the wall, and there would typically be a L shaped lead strip, flat on the roof, rising against the wall, and fixed into the mortar joint one bricj above (or over the lintel). I think lead lasts around 40 years, zinc less. If that's the trouble, roofers tend to use specialist leadworkers, or do their own small jobs. The deck may also have age related defects. Synthetic rubber coverings are now also used on flat roofs.
It's my guess that water is getting in where the roof meets the wall. This would explain damp running down the walls of the bay. It shouldn't be collecting at the foot of the wall, but the cavity might be choked with rubble.
These are all quite common problems. Silicone will not repair any of them.