High ammonia, high nitrates, but no nitrites

Just tested my water again today, and found that my nitrites dropped to almost nothing. Two days ago, ammonia was at 0.25ppm ish, nitrite was 5ppm, nitrates where around 40-50ppm. Ammonia and nitrates are about the same, nitrites are the only thing that dropped. This is my first saltwater tank setup (3 weeks old today); it is a 5 gal with live rock and sand. Have been trying to get my salinity down as well, which is perfect today. However, last night, I added more water to reduce the salt readings. The water has also been slightly cloudy for the past 1-1.5 days. Adding to the list, there is a cloudy film on top of the water, which I had a week ago, but it disappeared when I changed from an old HOB filter to a new one. I dont have a skimmer, but now I am considering. Does the nitrites, cloudiness, and film have anything to do with one another? Why are the nitrites gone, but ammonia is not? Thanks for the help in advance!