Significant color management changes were made in r152→r152, and lighting changes in r154→r155. The migration guide gives more information about each release. If you’re moving from r154 then the guide you want is probably this one:
Notably decay is different, and migrating would generally mean increasing intensity or decreasing decay. I suspect you’re seeing your ambient and hemisphere lights (which don’t decay) in the screenshot but mostly missing the spotlights (which do).