Welcome to the Q&A Forum

In glancing quickly at your first site, I see that Google isn't indexing it nor are any inbound links found. You need to have legitimate links pointing to the domain, not spammy links, to give it some creditability. If you get too many links too fast, this can also hurt you.

In regards to "How did they connect my sites together..?", Google has its own domain registrar which can see who owns what sites.

Hope this helps.

Try running your queries in Bing and see how it compares. If you see the terms you ranked for earlier ranking well in Bing, then you know you've been hit by a penalty in Google.

That's what made it clear for a site I'm involved with and have been trying to recover for many months now.

Hi Matias. Now that it's been a few months, I was curious to see if you were able to get your traffic back. Let us know if there has been some progress and what actions helped cure the curse.