i think it is more like Costia..
Which explains why you raised the heat a bit.
Important to know behavior of fish before they perished though too.If they simply get milky and die,then Costia may be the most logical assumption... but also need to know if there were other behaviors before
they showed cloudiness.Like restlessness,or being lethargic. Best to look at that before saying Costia.
Nitrates a bit high,and some of those species are sensitive (not so much Swords),so possibly stressing them enough to contract an infection.