There are some problems in those numbers, big problems.
Ammonia must be zero. However, you have a good thing here, with an ac. ic pH of 6.6 because in acidic water ammonia changes into the much less harmful ammonium. The Nitrosomonas bacteria will use whichever form is present. If you had live plants, they would help as they use ammonia/ammonium as their preferred source of nitrogen. Without plants, you are relying on the Nitrosomonas bacteria to deal with the ammonia, and it takes time for them to build up.
The next issue here is the nitrite that will occur at the second stage of the nitrification. It is zero now, but keep an eye on it, daily, in case it rises above zero. IF it does, a 50% water change daily should be done until it is zero. It may or may not appear.
Now to the nitrates. At 55 ppm these are way too high. This is likely a sign that things were let go for too long. Weekly partial water changes of 1/3 to 1/2 the tank should be done especially when there are no live plants. You have no other way to rid the tank of pollution. Read more here:
The cloudiness is a bacterial bloom and in itself harmless, though it shows the underlying issues which are not harmless. Provided nitrite does not rise, a weekly partial water change of half the tank will or should keep things better. However, the stocking may affect this; the more fish, or the larger the fish, the more critical are water changes to maintain stability, as that article will show.
Last suggestion, test your tap water for nitrate. This is a possible source, though from what you have told us I suspect here it is the fish load and infrequent water changes. Nitrates in an aquarium must be kept below 20ppm, and preferably not higher than 10ppm.