One of my ITs got "cloudy eye" & popeye at once because of a nitrate problem. I dosed salt and did two 50% W/Cs within 3 days and it cleared up in less than a week. It was pretty ugly too.
Anyway ya that's what I did and it cleared up fairly quick. I usually do a decent size water change once a month but just for now I'm going with a 15-20% every week and add salt just to be safe until I get back onto a normal schedule.