Happens with different cameras and different films, so it's likely related to development or handling? It doesn't happen on all my films and I'm using the same chemicals and process. The ghost is milky under transmitted light, brownish under reflected light. It's on most of the length of negative but not near the edges. My darkroom isn't *perfectly* sealed but this artefact doesn't look like optical fog?
It subtle on the (scanned) images so the effect isn't too bad. Any clue as what this could be?