Actually all altcoins are down, because people are transfering money from alts to Bitcoin.
I think that we can expect some, at least short term, spike in the prices of alts when Bitcoin will get into the expected correction. My guess would be that the Segwit2x fork might be a trigger for the correction.
This.

It's not only IOTA. Every altcoin is down because of the BTC wild pump and also because of the generally bad end of the year market.