Are my tropical fish tank readings at acceptable levels?

I've had my 180 litre tank set up for about 3 months now and everything was fine until last week, when my smallest Neon Tetra died.

Got home today to find another on floating on the top, one of my red tetras (sorry, so embarrassing but I can't remember the name - a lot bigger than a Neon!).

My water readings are:

PH 7.5
NH3 Zero
NO2 Zero
NO3 10

Are those within acceptable levels? There was no obvious disease on the fish so I have no idea what else it could be.

To complete the picture, the tank includes some bogwood, three living plants, 5 mollies, 4 Neon Tetras, 3 Clown Loach, 5 catfish (two algae eaters, the other three are bottom feeders), 5 Harlequins, 4 of the red Tetras whose name escapes me, 5 Black Widows and 5 Red Phantoms.