Welcome to Android Central! When you say you formatted them, do you mean you did a factory reset? The S2 is a fairly old device--remember, with how quickly tech advances these days, 2 years is a pretty long time. Apps continue to get bigger and require more RAM, so unless you're only using the apps from 2 years ago (without updating them to more recent versions), the current versions are probably taxing your system more.
You can always try wiping the system cache partition, which can sometimes improve performance, and won't erase any personal data:
http://forums.androidcentral.com/sam...2-s3-tab2.html