Yea why the melafix when there is no reason for it? Don't fix things that arent broken, too large water changes could mess up the cycle too, if your fish are stressed that would be my bet. Go look at your local river and see how muddy it is sometimes, it likely bothers you a lot more than the fish to be cloudy. Let it be for a little bit, allow your filters and cycle to catch up, do 50% max change in a week and use only prime. Cloudy tanks happen, depends where your water comes from (well water) winter tends to be a bad season for tap water as it is. As long as amo and nitrite are 0, and nitrates are minmal and ph is stable, just let it be for a bit. If your fish are stressing I would seriously test the aforementioned because maybe its cycling (though taking a second look at the pictures I don't feel its that, maybe a bacterial bloom).