No bug... published error/exploit for replay transactions was disclosed and Bittrex is in Maintenance Mode to secure the coins.

ZEN is the most profitable... because per calc and rate it IS THE MOST PROFITABLE. It fluctuates though.

If it helps anyone else... I put all my Nvidia miners back on ZEN and have been collecting as fast as I can without issue. Local wallet filling up nicely. I will have enough to run a secure node in a couple more days.