All my chemicals are good. They all stay withing range of the suggested levels on this site. I haven't had many problems over the last few years but at the end of last year i started noticing after about a week of not vacuuming the walls would start to turn yellow. its been the same way all year this year. Its really irritating because before I could go weeks without vacuuming and my water would stay crystal clear and i would vacuum due to leaves in the pool not because of the algae look to it unlike this year. Here is a pic of it starting to do it. it may be kind of hard to see. Any ideas of what could be causing this or what i could do to fix it? Thanks in advance!! 
