The cloudy water problems that you are experiencing are unlikely to be related to your home water filter. I would agree that the water conditioner that you are using is safe and also unlikely to be the cause of the clouding issues. There are several steps that I would take in managing your water quality issue:
i) take a fresh aquarium water sample to a local pet store that provides water quality assessment. This testing is usually performed free of charge and will alert you to potential water quality issues such as high ammonia levels, abnormal pH, or other problems
ii) check that your tank is large enough for the turtles that you have and that the tank filter that you are using is big enough for the tank capacity. Turtles produce a lot of waste and require much more water filtration than a fish tank of a similar size. Even the smallest of red-eared sliders need 35-50 gallon tanks, and as they grow their tank size needs to grow with them. Frequent water changes will be required even with adequate filtration.