Hello, I have a 22'x36' pond shaped inground salt water pool with vinyl pool coping and stamped concrete for decking. The pool has been in place for 5 years. This past summer, on the surface of the coping, I began to notice small (maybe dime sized) raised bumps on the surface of the coping. I'm trying to figure out what may be causing this issue. Is the concrete or rebar expanding and pushing on the back side of the coping? Anyone else ever face this issue? Thank you.