Fine debris (mostly seems to be tiny insect parts and vegetation) comes into the pool from the return lines when vacuuming. Is this a sign the sand needs to be replaced? It's only 3-4 years old and I'm sure we didn't need to replace the sand for approx. 6-7 years the last time. Thanks for any input!

Good afternoon all! Question and facts bolded below past the backstory. I have never been good at keeping the pool clean. A friend came over May last year to help me drain and clean the pool. I kept it running great til winter, then it sat and turned into a swamp. I have drained it again and it is currently filling back up. [B][U]Above ground 20' (I think) Vinyl lined pool.[/U][/B] My question is two part: 1) [B][U]Will the organic acorn/leaf/algae deposit stains go away after chlorine sits on them for a while?[/U][/B] Once the pool was drained, I tried scrubbing them gently with a pool brush and it took forever and a day to remove one tiny acorn stain, so I am hoping that once it fills up and chlorine gets in the pool, it will make scrubbing the stains away much easier. Also, I can remove the steps and pressure wash them. 2) [B][U]Are bags of shock good enough to get my pool balanced after filling with water from the spigot, or do I need to go to Ace (closest pool store barring an hour drive) and get some 'start-up formulation' or something?[/U][/B] Thank you so much! PS. The attached pics may be hard to see at the resolution, but basically the large brown ring around the perimeter is the leaf deposit ring, the brown dots all throughout are acorn/leaf deposits, and there is black speckling (specifically pic number two, at the foot of the steps to the right) that is sediment I was not able to completely remove before I gave up trying.