You might want to try CarlD's trick of adding a handful of DE to your sand filter in case the cloudiness is caused by something too fine for the sand to catch. He recommends that you add just enough DE to raise your pump pressure by no more than 1 psi--and that rise sometimes takes a little while to register--and then see if it helps. The DE will wash out when you backwash, so if you add too much, you can backwash it out and start over.

Keep filtering, keep the Cl high, and keep us posted!
Janet