I left my pool open for the first time all winter and now I have yellow stains. The stairs, skimmer, returns, baskets, and even the liner all have a yellow tint. I had a lot of leeves fall in the pool and wasn't able to remove them for over a month. Could my issue be tannins? I am torn between tannins or iron. Your thoughts? You can see in the last pic where the liner is actually unstained where leeves had piled up. Liner appears lighter in that spot.