I am beginning my 6th season as a pool owner. This was the first time there was a softball sized orange/rust colored stain in the deep-end of the pool after I did my initial cleaning. My pool opened quite clean (it always does) with the exception of a few leaves and several worms and bugs. The water is always quite clean after 7 months of dormancy. This was the first time there was a “stain” though. This is in the deep end of the pool and brushing it has zero affect. I have yet to manually get close to the stain to try and clean it (water is only 62 degrees!) but I will try soon. However, I have a feeling it is going to be a stubborn stain. Any suggestions? Thanks!