Lee, I think what Christy meant is this:
Most recreational divers in Cozumel follow a generally standard profile - 1st-dive 70-80 feet, 2nd dive 40-60. I would venture to say up to 70% of shops and recreational divers follow profiles very close or similar to this, I'm sure most of Scuba Mau's trips do too. On a standart profile like this, a downdraft or downcurrent might take you from 80 feet to 110-120 or from 60 feet to 80-90. There are no downdrafts that take you from 80 feet to 300, period. I think this is what Christy was trying to say.
Like most here, I do not know any details of the dive plan, so anything I say is pure speculation, if downdrafts were a factor in what happened, and considering they were on a non-client private trip, it’s probably true that they were doing a deep dive to being with, which could have been aggravated by downcurrents. Again, this is merely speculation.
I too have prayed for them, and hope they make a full recovery.