Yesterday = 2nd page, Today = Nowhere....Sandboxed?

There's something going on with google. Since middle of March some of my sites go up and down. And since today - gone deep into the index (one site from No.1 to ??? from more than 50 Mio indexed sites for that keyword). That site was stable for the last 9 month. With another site (100 percent white hat blog) since middle of March I don't get new articles indexed anymore (before nearly in real time)...

Even on some other forums I find similar postings that people have problems since middle of March. Some start speculating about caffeine now...

I'm wondering, I don't find anything here about that...

same here

site from No.5 - deindexed

i submitted it in 150 bookmarking sites and get indexed again
and already receive traffic from google