Not all, but as we can see majority of alts are negative at the moment.
My take on this is; people are dumping alts and converting them to BTC, so they'll get their hands on BitCoin Gold when BTC forks on 25th Oct.
Also, it looks like BTC is currently heading upwards which means people can pull their money out from alts, sell BTC for profit and wait for fork to buy back in when its cheap. What's your take on the current scenario?