The recorders stopped 1 minute before the call that they were ditching. I doubt anything occurred at this time which could have tripped the "G" switch.
My money (and I'd put it where my mouth is) is generator failure with the APU not started. I've seen it happen and assure you that in good VMC the APU is the last on your list of priorities! You certainly wouldn't be concerned about the CV/FDR! I'm sure the absence of data will be a slight hinderance to the TSB, but not greatly so. I'm sure that the absence of CVR in the last 30 seconds will be a great bonus to the TSB investigators' future lives
