I am not sure but I think the decrease in the price of the bitcoin is only ly due to the DASH and the ETH Because with the rapidly increase in the price of these two altcoins the people attracted toward these two altcoins and after sell the bitcoin invested their money in the ETH and DASH that made the unlimited available amount of bitcoin in the market of internet .
Second thing that may be the possible reason is the unlimited of bitcoin Mining ( which is controlled but mining of two types, I don't know much about this hope anyone can explain us for such thing in better way ,I am waiting ) to make the bitcoin as better service for the bitcoiners .
Edited:
https://bitcointalk.org/index.php?topic=1840367.0;topicseen
Here I posted the link that may be a big reason to the drop in the price ( it is actually the same topic for which I was waiting )