How commendable that you're trying to do right by these turtles!
You needn't have bought the 10 gal and should have put them immediately into one of your larger tanks.
The water is cloudy because there are way too many creatures in the tank. I would put them in the bigger tank now.
I had 4 red eared sliders for about 16 years. They need a large variety of different foods and many of them bought at the size of yours do not survive due to improper diet.
Please go to the following forum. It's all about turtles and there are many experienced people there who can answer all your questions!