My grout at the waterline that is right under the coping has seperated from the coping allowing water under the coping. Do I need to just redo the grout? I'm wondering if I have to use something additional to make sure no water can get under the coping. I'm hoping I dont have to remove all the coping and re-thin set it so it's full covered on the bottom and can't let water in. Thoughts? Advice please!!