Help with possible leveling kit

Hey guys,

I need a little help. I'm by no means a mechanic so I am a little in the dark here. My 2012 tacoma baja edition is sagging a bit in the back as in the ass end of the truck is resting lower than the front. I recently put a heavier duty rear bumper on it and I believe this is the problem. Would getting a rear leveling kit for it fix the problem or should I do something else?

Thanks