[Q] Note 3 is unstable after half day usage topic

I notice after back from work about half day, with heavy usage but still I check the RAM only used about 1,5 GB to 2 GB, but the phone performance become sluggish, I watched using mx player or BSplayer the frame rate is horrible when I play the game I have noticeable lag. I don't know what is the causes because my old note 2 is never have a problem like this.
My note 3 still using latest 4.4.2 update and note 3 type SM-N900, unroot, no heating problem,no battery problem.
Any advice?

xda-developers