Sorry to hear about your traffic drop. Unfortunately I think this type of question is too broad for you to get an answer in a forum. There are so many possible reasons for the traffic to drop. Here are a few:
-The initial traffic boost could have been from the "honeymoon affect".
-Do you have content that is taken from other sites or otherwise duplicated? If so, then Panda could have affected you. Have a look at your organic traffic and see if it drops on a known Panda update day.
-If you built links with too much anchor text and from easy to get sources then Penguin could have affected you.
-You could have issues with your server
-You could have malware
-You could have competitors with better SEO.
