My Turtle Has Cloudy Eyes, What Should I Do?

I have an alligator snapping turtle. He was born in November 2008. Just within the last three weeks his eyes are cloudy why? He seems to be eating the same lots of pellets and fish the person i bought him from said that a good diet and he should be getting all the vitamins he needs. also he seems as active as always. everything i have read says he should be sick is this true. i was told to treat him with a fungal infection he had some white spots by his tail. after a week of treatment nothing has changed. not really sure why his eyes are cloudy or what i should do about it now. if you have any ideas as to what this could be please let me know. everyone also said it should not be a lightning issue because alligator snappers live in murky water anyway. thanks miles