I would just reduce the volume you currently have. That will be enough to stave off muscle loss, but enough to keep the muscle strong.
As far as bringing up a lagging part, I like to alternate between training the muscle 1x/wk and 2x/wk. Obviously, the intensity will have to be reduced on the 2x/wk sessions, but this is will increase the overload on the muscle and provise a new stimulus for growth. Also, make sure to really focus on the eccentric portion of every lift.