My pool was installed 7 years ago and now a couple of the interlock bricks around the edge of the pool have come lose (specifically the bricks that sit on side of the plastic pool steps). What is the best method to secure the bricks back in place?

The edging bricks overhang the edge of the pool by 1-2 inches all around, so they must be secured. The rest of the bricks in the patio are simply held in place by the sand between the joints.

The fact that only the bricks by the plastic steps have come loose makes me think whatever was used to secure them 7 years ago did not bond well with the plastic...