I used to Rank No.1 on Google

Happens to me as well. Just get your backlinks up and you should see results.

 

I recently hired a person to submit my site to 100 directories, maybe that has triggered the Penalty.

 

I think google has improved the ranking algorithms a lot. In the meantime, there would be many technical glitch. My suggestion is just focus on building quality and relevant links. I Hope this helps.