In thinking about your situation, I think a crack in the top step wouldn't indicate a problem crack in the gunite, especially after 8 years. A movement crack in the gunite would show somewhere else, not in the step area. You can try to listen to the tapping sound with the water still in the pool.
But I really don't think you have a serious problem. Try using a dye like food coloring and check for a leak. If a delamination issue, and if other areas don't show cracks soon, then it would be an isolation issue. You could simply trying placing some epoxy cement into the crack and let it be for now.