Motorola Droid Razr Slow Down

Hi there,
I'm using motorola droid razr xt912 and 4.1.2 orignal rom is installed on it but its sucks
Droid Razr Got 1 GB Ram I used many other phones with 1 GB ram but the run fine
As I Think 1 GB Ram is fine enough and phone shoudnt lag with 1gb ram but xt912 just slow down and many of the time it stuck when even i start any app
I Think the orignal rom which is installed is problem.
I'm right guys ??

So Guys Is that problem is just coz of rom ???
And which rom is stable for droid razr xt912 ??