Well, I am happy to hear that milky-colored urine is normal! What kind of greens do you mean? Lettuce? Iceberg lettuce has little nutritional value. Romaine lettuce, perhaps?
Or maybe kale?
A litter box? Great! The cat litter I use is called Fresh Step and it has deodorizing chemicals in it. It is great at absorbing odors! The chemicals will not harm the rabbits? They won't eat it, will they? They like to chew...
All lettuce is fine, even iceberg. It is more for a treat than for balancing the diet. Kale, timothy hay, alfalfa are all good.