You have not successfully flushed the head. When you say you've "run the solution through the head" please explain. If you had actually done that it would be red instead of Light Black.
What you need to do is upgrade your firmware, boot the printer into maintenance mode, and do a series of strong channel pair cleanings/purges for the channel pair that the LK position is in. This will clear the air block that is in your damper. You will know that it's getting through the damper if the LK goes red.
However, if the same exact nozzles are still out after actually flushing your head, then you know that those nozzles are shorted.