Did you tried to check with Activity Monitor as to what these unnecessary apps are? IMO, they could be widgets or an app that is running in the background and stealing RAM for the OS X purpose. Memory Diag is free for limited usage utility that can help you optimize RAM usage on system. You can check this app from App Store Meanwhile you can clear caches and temporary files from the startup drive. Goto /Library/ folder to clear RAM. Force Quite apps like Safari, Chrome or Firefox. Run free Mac cleaner software to clear out leftovers, logs and other junk data. You can download and use free version of Stellar Speedup Mac software. Even if you face the issue again then you might need to reinstall OS X. I would recommend a clean install of the OS X. Hope this helps!!!