Noting their location adjacent the bridge and the pompoms they could be something else than an exhaust.
I can't imagine that would be an ideal location for an exhaust, which would inevitably cause exhaust to pass across the bridge wings, pom poms and so on.
It's worth considering they might be air intakes for the hangars.
Another feature which might be galley exhaust could be the funnel openings, on both sides, on both funnels, just below the top lip (visible in the crane photo among the IWM photos).
Whatever they are, they're a feature new to me!