Inside speculation from those who've seen the Blues' own video is G-LOC during an aggressive formation re-join. Closure speeds are quite fast, thus heavy G's are pulled to get back in 6-plane delta formation quickly.
Whether #6 was out of position prior to this, forcing a late & hurried rejoin, will be up to the board to determine.
Sad day for the Blues and the whole USN. I've watched you guys since Cleveland in the 40s - you bring poetry to the sky.