This is what build up in a salt cell may look like. This happens to be the Penatair intelliChlor cell (IC-40) to fix this, the cell should be cleaned with the garden hose, then rinsed through with a solution of muratic acid and water (see your owners manual for specifics of how to, and how often!). If you do that, and put it going again, you should see a difference with your well chlorinated pool water!
