Grass in rocks

New to home owning, bought this house and it came with rocks in the front, didn’t know I was supposed to spray it regularly with weed preventer.

Now I have lots of grass/dead grass and weeds in the rocks, they have broken through the degraded barrier beneath the rocks.

How do I remove all the grass/dead grass from the rocks? I tried to hand pull it but the grass just breaks and the weeds are grown so deep in the ground. I’ve also tried using a weed eater and it just takes the top off.

Not sure what to do any help is appreciated