For the simple explaining is because of the price of bitcoin is going down, so all of the alternative coins follow the bitcoin's price too, we know that the bitcoin is main digital coins, it is first digit coin in the world be used for price reference to all of the alternative coins. For the complex explain about the alternative coins price is going down, it depending on the aspects of fundamental alternative coins due to right now not all of alternative coins are going down, we can see dashcoin is up trend although the price of bitcoin is down, don't be fear the price will be going up again.