There are a number of reasons. The alt coins are definitely responsible as more people are moving to alt coins and thus the total money invested in crypto is getting divided. There are a lot of other reasons that care causing the decrease in price. For instance, just like Facebook , Google has also announced that will ban crypto related ads from April 2018. There is still one month left but the negatives news is already a source of trouble to people associated with crypto community. Google has done this thing in past for other suspicious projects and they were badly affected.