Well, exactly 5 days ago something strange did indeed happen at bittrex - some people say it was upBit buying alts at a discount from bittrex, some say it was bittrex moving alt fees into BTC, some say it was just a colossal mistake. It's still not clear what happened.
So yes, it does seem very strange, but if you check data 1, 2, 3 months old it will be much less wild.