Splitlip:Jupiter diver here with one small point which may have relevance. The current is often much too fast to swim against. Buddies hook up when one stops, takes finger or gets low. The up stream buddy drifts to the down stream buddy.
I have lots of experience in currents too strong to swim against. The key to buddy teams staying together is to never get apart. In my opinion, this particular separation was the result of Lee descending when Joyful was unable to descend. He deserted her. The last time I was in Jupiter, conditions were far from ideal. On the first dive Nancy had difficulty equalizing. We made the descent together at her pace. On the second dive, she had no trouble equalizing, but upon noticing we had only 2 feet of visibility, we deployed a buddy line to take no chance of separation.