The driftwood and plant should be a plus for the tank.
I see by your readings they are 0 straight across the board. If the tank is cycled you should have at least a little Nitrates.
See any white spots? ICH looks like grains of salt.
Is there any rapid breathing or reddening of the gills? Does the scratching seem to be focused around the head area or the sides/belly of the fish? What kind of sand is in the tank? Is there any suspended particles in the water/cloudy water? Did the scratching start shoon after performing a water change?
I'm not thinking Ich but Ich will last until effective treatment of it is carried out. Sometimes months. The best way to cure Ich is simply be raising the temps.
Do the fish eat & poo normally? Does the poo look as it should or is it white, stringy, red or segmented? Are any of the fish large enough for you to remove from the tank & get a good look at the gills? You would specifically be looking for darker red gills than usual or white/pale patches in the gill material. Checking for rapid breathing is easy just watch the fish very closely to see if the gill covers are opening & closing more rapidly than normal. Are there any visible parasites on the fish or do the fish look like they have a fine gold dust coating over thier bodies?
Normally fishes gills would be a nice bright mid-toned red. Gills that have pale pink patches or are very dark red, like blood, could be a sign of a gill parasite. If the fish are eating & pooping normally it probably isn't an internal parasite. If there's no gold dust coating it isn't velvet & if there are no larger parasites visible it's safe to rule them out to. By process of elimination I think you would be left with a gill parasite or irritation from the sand. My money is probably on the sand as playsand often has sharp grains that fish can find rather irritating.
Without personally removing the fish inspecting the gills I can't say for sure if there is a gill parasite present or not. Gill parasites are often accompanied by the fish shimmering (shaking in one spot), rapid breathing & rapid darting movements. If those symptoms are being displayed as well then a gill parasite is a distinct possibilty & it may pay to remove one of the larger fish & very carefully open up the gill covers to inspect the gills with a magnifying glass. If your not confident enough to do this yourself you might be able to get a really good LFS that you trust to do it for you. There are plenty of different sorts of gill parasites & you need to ID the correct one so that you can get the right medication to treat it.
I have had playsand with Mbuna before & it did irritate them to the point that the sand had to be removed but that may just have been the particular brand of playsand I was using. If the grains are not rounded though it would probably be wise to change to Pool Filter Sand or some other round grained sand. Even if that is not the problem it will prevent more irritation & injury of the gills.