Retaining external wall. Seeping and bubbling

[Gemmafenwick84]

We have a retaining wall at the front of our house that is shared with the neighbours. The wall is painted in masonry paint. Over the years we get yellow seeping areas, we thought they were stains from water trixkling down the from the balcony above. When we painted the wall annually we added some zinnser to those areas before adding the paint. The paint has bubbled in areas and we can feel the water inside those bubbles and the yellow water trickles out. Any ideas why this is happening the bubbles and stains. I'm thinking it's maybe the water getting in from the 'balcony area' above in the pointing and then just finding a way out of the wall somehow. Should there be weep holes or something. Can anyone advise the type of Trades person needed to look at this. Don't know where to start or whether to be worried. Thanks

[Someone-Else]

Looks like rust, from the railings above.

[big-all]

i assume its happening both sides as the build/adaption looks done as one
if not i wonder iff a different treatment [stain blocker /railings treatment/paint type ] to next door have you asked
i assume from the railings as well but could be rebar/other metal not seen