I have an in ground concrete pool that is approximately 22 years old. I have some small little, round stains throughout the pool that will not come out. I’ve tried scrubbing them with a chlorine tablet with no luck. They are about the size of a pea. Secondly, I have some stains, on a larger scale, also throughout the pool floor. These stains look like dirt stain, however, will not come clean. I’ve tried scrubbing when I shock the pool with no luck. These stains are scattered throughout the pool but they are not covering the floor totally. The first 2 pictures I attached are depicting the larger, dirt looking stains. The last picture, next to the umbrella hole, is of the small, pea size stain. I recently bought a bottle of Suncoast stop stain which didn’t do anything at all. Any advice would be greatly appreciated!!