When you changed bars you changed the cable length slightly. (For example if you didn't get the cable housing seated back the same way it would change the cable run.)
Assuming there wasn't some other problem before you changed bars, you just need to readjust the RD. Playing with the barrel adjustor will likely take care of it.
__________________
You could fall off a cliff and die.
You could get lost and die.
You could hit a tree and die.
OR YOU COULD STAY HOME AND FALL OFF THE COUCH AND DIE.