When I was recently grouting a bathroom, after I had applied the grout and cleaned off with a sponge, down along each grout line there was what looked like a crack down along each joint, was this because grout was too wet or am I removing too much grout from the walls with the sponge. I waited about 5 mins before I cleaned with the sponge. When grout is mixed should you wait awhile before appling to the walls.