I occasionally have that problem and I usually put a charcoal pad in my filter for a couple of days (while suspending ferts) until the water clears up and then remove it and continue as normal. This has always worked for me. Just remember that charcoal will take out any ferts in the water as well as reach a point of saturation and need to be removed, not that charcoal is recommended to be kept in planted tanks for the long term. A charcoal pad costs about $3 where I live. A UV filter would be even better but the cheapest one I could find was about $50.