Hi Mof3kz,
Whenever I had to deal with a similar situation to yours I was always checking what we have done, what did change in the past few weeks.
Even, if you have been working with some great link partners, take your time and write an email. Ask them if they have experienced a fluctuation lately in the search engines on their ranking.
Possible situations:
1. The major link partners have experienced big fluctuations, maybe their links profile had a bigger change and since you are connected it will in some way effect you too.
2. They didn't experience any fluctuations: this is when you ask yourself, ok, then what the hell happened here? Stay chill! try to get on-site ask yourself if you are optimizing the right way. Try to avoid any possible issue from your site, add better content if possible, check for crawlability, etc. etc.
3. The link partners tell you they have experienced some kind of fluctuations, but not big ones. Now this part is tricky. As we all know, search engines like Google are constantly changing the algorithms, trying out new filters to show up the most relevant content. Some filter (new or existing one) has triggered out your possible loss. It might be temporary, it might be something stable. In these cases I usually advice the same thing as @ the point 2.
I hope this resolves your situation! Good luck!
Gr.,
Istvan