There has been a drop in Black support for Obama and the Dems. Not big movement but noticable nonetheless.
Iirc Romney actually got something like 19% of the young Black male vote in 2012. So there is some chipping away at the margin, which if its a trend might start making a difference a couple elections down the road.
That 19% number might be a little high, but not by much.
I checked the NBC exit poll for 2012.
All Blacks (age 18-29): 8% for Romney
There was no gender data for the individual age groups.
I know that young Black women voted almost 100% for Obama, so your number is close.